JP2911005B2 - Processing method of bump electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for processing bump electrodes, more specifically, a semiconductor chip for connecting electronic components such as semiconductor elements by a wireless bonding method such as flip chip bonding and tape carrier bonding. The present invention relates to a processing method such as a reflow process and a bonding process for bump electrodes formed on a substrate and a substrate.

(Prior art and its problems) A bump electrode formed on a semiconductor chip or a substrate is subjected to a reflow process of heating and melting in a state where an organic liquid (flux) is applied to make the bump electrode spherical, and thereafter, the bump electrode is formed. Also, in the bonding step of bonding the wiring of the substrate or the semiconductor chip to the substrate, a process of applying a flux and heating and melting again to remove the oxide generated on the outer periphery of the solder bump and to increase the bonding strength is performed.

However, when the bump electrodes are heated and melted to make them spherical, a phenomenon of a solder flow in which the solder of the melted bumps flows along the wiring occurs, and the height of the bump electrodes decreases, or the height of the bump electrodes varies. Will be.

Therefore, it has been conventionally proposed to form a solder dam around the bump receiving portion on the wiring in order to prevent the solder flow (Japanese Patent Application Laid-Open No. 60-93670). There is a problem that becomes high.

In addition, a method of providing a solder flow stopper narrower than the bump receiving portion between the bump receiving portion and the wiring portion has been conventionally proposed (Japanese Patent Application Laid-Open No. 1-145630). There are disadvantages such as an increase in the current density in the wiring portion and a complicated wiring.

The present invention solves the above-mentioned conventional problems by changing the manufacturing steps and the bonding process of the bump electrode without changing the wiring process and without complicating the wiring structure. It is an object of the present invention to provide a processing method capable of preventing the occurrence of the above.

(Means for Achieving the Object) Such a processing method of the present invention provides a method of forming a Pb, In, Sn
A coating layer made of any one of the above elements or an alloy containing the same as a main element, and an oxide film layer of the coating material is formed on the coating layer, and any one of Pb, In, and Sn is mainly used. Forming a solder bump as an element on a bump receiving portion on a coating layer, and then subjecting the solder bump to a spheroidizing process by heating, the melting temperature when the solder bump is heated and melted; Is set to a temperature lower than the melting point of the coating material, and the flow of solder is prevented by an oxide film layer around the solder bumps.

Thus, the melting point of the coating material refers to the liquidus temperature when the material is pure Pb, In, or Sn containing unavoidable impurities, and the solidus temperature when the material is an alloy. Say.

(Function) According to the present invention, when the bump electrode is heated and melted in the reflow treatment or the bonding step, the oxide film layer of the coating material remains without being destroyed and removed by the flux, and the oxide film around the solder bumps is removed. The layer itself functions as a dam with poor solder wettability and prevents solder flow.

(Embodiment) An embodiment of the present invention will be described with reference to the drawings. The embodiment shows a case where bump electrodes are formed on a substrate. In FIG. 1, (1) is a substrate, (2) is a metal wiring, and (3) Is a coating layer,
(4) is an oxide film layer, and (5) is a solder bump.

The substrate (1) is made of ceramic, glass epoxy (polyimide resin), or the like. Wirings (2) such as Cu and Ni are formed in a predetermined pattern on the substrate (1).

The coating layer (3) is made of high-purity Pb, In,
Pb- with any one element of Sn or their main elements
It is a layer formed of an alloy such as Sn, Pb-In or the like. The wiring (2) is formed by electrolytic plating or electroless plating, vapor deposition, or the like.
Formed on top.

The oxide film layer (4) is an oxide formed by forming the coating layer (3) and reacting the surface of the layer with the atmosphere. When the coating material is Sn, a Sn oxide film, Pb-Sn The alloy is a Sn oxide film, and the Pb-Sn alloy is an In oxide.

The solder bump (5) is a solder material containing any one of Pb, In, and Sn as a main element, and is preferably proposed by the present applicant first (Japanese Patent Application Laid-Open No. 63-301535 and Japanese Patent Application No. Hei. 340132)
Use alloy wire.

That is, the solder material was prepared by a rapid solidification method in which any one of Pb, In, and Sn was used as a main element, and additional elements such as Be, Ag, Sn, Cu, Ni, In, and Sb were added thereto. It is an alloy wire consisting of fine wires.

By using the above-mentioned wire, the solder bump (5) can be bonded onto the predetermined bump receiving portion (3a) on the coating layer (3) by a thermocompression bonding method (ball bonding) using a wire bonder. it can.

The thermocompression bonding method includes not only means of thermocompression bonding alone but also an ultrasonic combined method of thermocompression bonding while applying ultrasonic waves,
By this thermocompression bonding, the solder bump (5) breaks and removes the oxide film layer (4) on the bump receiving portion (3a) of the coating layer (3), and is directly bonded on the coating layer (3) as shown.

Thus, on the substrate (1), a bump electrode (5a) is formed which is electrically coupled to the wiring (2) via the coating layer (3).

Next, the bump electrode (5a) is subjected to a reflow process to make the shape spherical, which is shown in FIG.

The reflow treatment is a step of heating and melting the solder bumps (5) by applying a flux onto the base (1), and at this time, the melting temperature of the solder bumps (5) is set to a value of the coating layer (3). A temperature lower than the melting point of the material is set, in other words, a solder material having a melting point lower than the melting point of the coating material is used as the solder bump (5).

For example, when a solder alloy close to the PbSn eutectic composition is used for the solder bump (5), the coating layer (3) is formed by plating Sn (melting point: 232 ° C.), and the solder bump (5) is formed at 220 ° C. lower than the melting point. ) Is heated and melted. When a high-temperature solder material of Pb-Sn alloy (melting point of 232 ° C. or more) is used as the solder bump (5), Pb-5 wt% Sn (melting point of 305 ° C.) or PB
Using a coating material of −10 wt% Sn (melting point: 260 ° C.), the solder bump (5) is heated and melted at a temperature lower than the melting point of the coating material.

Further, when a PB-In alloy solder bump (5) is used, a coating layer (3) is formed by vapor deposition using a Pb-10 wt% In alloy (melting point 300 ° C.) as a coating material, and a Sn-In alloy is formed. When an alloy solder bump (5) is used, Sn or In is used as a coating material.

The bump electrode (5a) is then heated and melted again as a pretreatment in a bonding step for bonding the semiconductor chip (6) (FIG. 3). A flux is applied to destroy and remove the oxide (5 ') generated on the outer periphery of (5), and the solder bump (5) is heated and melted at a temperature lower than the melting point of the coating layer (3) as described above. .

FIGS. 4 to 6 show test results for confirming the operation of the present invention described above.

In the test, the wiring (2) was Cu and the coating layer (3) was Sn (melting point 23).
2 ° C) by electroless plating and solder bump (5) with Pb-40wt% Sn-0.4wt% Cu-0.4wt% Ni-5wt% A
The bumps were thermocompression-bonded using g-1 wt% Sb by a bonding method, and then subjected to a reflow treatment. FIG. 4 shows a state before the reflow processing.

In the above reflow treatment, a melting temperature of 220 was applied while applying α5003 manufactured by Nippon Alpha Metals to the flux.
FIG. 5 shows the result of heating at 30 ° C. for 30 seconds, and FIG. 6 shows the result of heating the solder bumps of the same material at a melting temperature of 250 ° C. for 30 seconds. In FIG. 5, it was confirmed that the oxide film layer remained without being destroyed by the flux, and that no solder flow of the solder bumps was observed.

On the other hand, according to FIG. 6 heated at a temperature higher than the melting point of the coating material, the oxide film layer was broken, and the solder flow occurred there.

Although the above embodiment has been described with reference to the case where bump electrodes are formed on the substrate (1), it will be easily understood that bump electrodes may be formed on the semiconductor chip side.

(Effects) According to the present invention, when the bump electrode is heated and melted to make the bump electrode spherical, the oxide film layer itself on the coating layer itself has a function of a dam for preventing the flow of solder, so that a solder dam is separately formed. Since no process is required and there is no need to form a narrow constricted portion in the wiring portion, the productivity and the current density are not increased, and the durability and reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view illustrating the formation of a bump power pole in the present invention, FIG. 2 is a partially enlarged cross-sectional view illustrating a reflow process, FIG. 4 to 6 are enlarged perspective views for confirming the operation of the present invention. FIG. 4 shows a state before reflow.
FIG. 5 is a test example according to the method of the present invention, and FIG. 6 is a comparative example. In the figure, (1) ... substrate (2) ... wiring (3) ... coating layer (3a) ... bump receiving part (4) ... oxide film layer (5) ... solder bump

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-1-202830 (JP, A) JP-A-1-205551 (JP, A) JP-A-64-37039 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) H01L 21/60

Claims (2)

(57) [Claims] A coating layer made of any one of Pb, In, and Sn or an alloy containing the same as a main element is formed on a metal wiring, and an oxide film layer of the coating material is formed on the coating layer. Generate
Pb, In, forming a solder bump having any one of Sn as a main element on the bump receiving portion on the coating layer, and then heat-treating the solder bump to form a spheroid bump electrode processing method, A method for processing a bump electrode, comprising: setting a melting temperature of a solder bump to be lower than a melting point of the coating material when the solder bump is heated and melted; and preventing an oxide film layer around the solder bump from flowing the solder. 2. The bump electrode according to claim 1, wherein said oxide film layer is formed by forming a coating layer on a metal wiring, and said solder bump is bonded to said bump receiving portion by thermocompression bonding. Processing method.