1. Field of the Invention
The present invention relates to a semiconductor element and a producing method for the same, and a semiconductor device and a producing method for the same, more particularly relates to a bump structure of a flip chip type semiconductor element mounted face down and a producing method for the same, and a packaging structure thereof and a producing method for the same.
2. Description of the Related Art
As a connection method for connecting an electrode of a semiconductor element and an external terminal, there are two types of methods consisting of a bonding wire method using a metal thin wire and a flip chip method using a solder bump formed on an electrode of a semiconductor element. And the flip chip method is considered to be advantageous in a high-density and a high pin count tendency in recent years. In order to raise a packaging density of a semiconductor package in recent years, a ball grid array type semiconductor package with a solder bump formed as the external terminal is used abundantly as a technology which can respond to a high pin count tendency, keeping a terminal pitch large. A flip chip type is adopted also as a semiconductor element mounted to a packaging board (Interposer) in many cases. As this flip chip type connection method, many are developed. For example a connection method referred as a control coraps chip connection (C4) is mentioned first.
FIG. 35 is a cross-sectional view showing a conventional structure of a flip chip type semiconductor element. As shown in FIG. 35, on a semiconductor substrate 1, an electrode 2 which is connected to internal wiring and a cover film 3 having an opening on the electrode 2, is formed. And on the electrode 2, a solder bump 20 is formed through an interconnected film 4 and an adhesive film 5. As for a method for forming a solder bump 20, it is common to form a hemispherical bump by supplying solder by various methods such as an evaporation method, an electrolytic plating method, a solder paste printing method, and a solder ball loading and supplying method, and solder reflow process using flux.
FIG. 36 is a cross-sectional view showing a conventional flip chip packaging structure of flip chip type semiconductor element. On a pad 14 of a wiring substrate (Interposer) 12 wherein the pad 14 and a solder resist film 13 are formed on the surface, solder is supplied beforehand. Then, after applying flux, a semiconductor element is carried on the wiring substrate 12. And connection between bump 20 and pad 14 is completed by solder reflow process to form a solder fillet 11. Subsequently, the crevice between the wiring substrate 12 and a semiconductor substrate 1, which is not shown, is filled up with underfill resin.
A method for using bonding wire and forming a gold stud bump on the electrode of a semiconductor chip, in addition to a solder bump, and a method for forming a gold bump by electrolytic gold plating are conventionally known. These bumps are adhered to metal films such as gold plating, silver/tin solder, and indium/tin/lead solder formed in the wiring substrate side.
For securing reliability, filling up the crevice between a semiconductor chip and a wiring substrate with underfill resin after flip chip mounting is carried out. When resin filling is performed, keeping the crevice between a semiconductor chip and a wiring substrate large is preferable for performing good filling without generating void. However, if a solder bump is required to be formed highly in height so as to be melted on an electrode and shaped in hemisphere form, the amount of solder to be supplied should be increased. This makes it possible to short circuit to an adjoining solder bump, between the electrodes having a fine pitch. Therefore, it is becoming difficult to form a solder bump with height on an electrode with advance of a fine pitch tendency. On the other hand, since, as for the fine pitch tendency, filling resin stream is narrowed superficially, the difficulty of filling of underfill resin is accelerated by fine pitch.
A method for forming a solder bump by an evaporation method and a solder paste printing method involves an increased manufacturing cost, since a durability of a mask is scarce as well as requiring the mask.
Also, a solder ball supplying method involves a comparatively high cost of the solder ball per se, and needs equipment wherein a solder ball is aligned in a required layout and carried on a semiconductor chip. Since package loading in a wafer unit is difficult, the bump formation cost as total becomes high. Moreover, manufacture of solder ball with further small diameter corresponding to a fine pitch is difficult. Then, the smaller the required ball size (diameter) becomes, the more the manufacturing yield falls, incurring an influence on high cost.
Furthermore, when there is an electrode arranged on a memory cell, and when solder is used as a bump material, alpha rays generated from a radioactive element contained in a lead which constitutes solder or tin may cause a soft error.
Also, there are the plating bump and stud bump using gold. However, problem such that cost of gold materials is high is posed. There is also raised a problem such that the more the number of bumps increases, the more formation cost increases also, in order to carry out individual formation in a gold stud bump.
Furthermore, when solder junction of the bump which used gold plating is carried out, since gold has a good wettability, solder is getting wet upwardly on side surface and enters from the interface of an electrode and gold plating. This may result in the fall of interface intensity, or exfoliation in the end, involving the problem on reliability.
Also, a soldering technique by use of a plating bump using copper is also proposed. For example, after forming a copper bump by an electrolytic plating method, forming the polyimide film on a semiconductor board so that the upper half of the copper bump may be exposed, and forming a solder film on the copper bump by dipping method is disclosed in JP-A-3-22437. However, with a flip chip coated with a thick resin film in this way, when mounted on a wiring substrate, it becomes difficult to be filled up with underfill resin. In addition, since an adhesion nature of the copper bump and the polyimide film is low, unless processing special to the copper bump side is performed, solder easily gets wet, spreading to the electrode. Problem on reliability is thus raised similarly to the case of a gold bump.