JPS61147540A - Etching method of bonding pad of semiconductor element - Google Patents

Abstract

PURPOSE:To prevent a bonding pad from forming a different film by dipping a wafer in a liquid of etching aluminum, and energizing an ultrafine DC to the liquid to etch. CONSTITUTION:Two electrodes 2a, 2b are inserted separately into etchant 105 in an etching bath 104. The electrode 2a is platinum, the electrode 2b is alumi num, the electrode 2a is connected to ultrafine negative DC current, and the electrode 2b is connected to ultrafine positive DC current. Metallic ions (posi tively charged) and impurity ions generated in the etchant are attracted to the platinum electroded and neutralized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an etching method for bonding pads of a semiconductor device, and particularly to an improved liquid phase etching method for bonding pads before bonding.

[Technical background of the invention]

Conventionally, in the formation of bonding pads for semiconductor devices, an aluminum layer is deposited to form a wiring pattern including the bonding pads, and then this PSG (phosphosilicate glass) layer is deposited and ammonium fluoride-based material is used for buttering. Etching is performed using an etching solution, and at this time, aluminum is also slightly etched.

The above liquid phase etching is generally carried out using an etching solution [(1 (■)) as shown in FIG. 3, and a semiconductor wafer carrier (10
2) A plurality of semiconductor wafers (103, 103...) (hereinafter referred to as wafers) housed in a wafer carrier (hereinafter referred to as wafer carrier) are immersed in an etching solution (105) of an etching bath (104). Etching was performed while rotating it. Note that the rotation of this wafer carrier is controlled by rollers (
106) was slid into contact with a wafer whose peripheral edge was partially exposed at the bottom of a wafer carrier.

[Problems with background technology]

According to the pick-up method, for example, 1.0
The etching of the PSG layer provided with a thickness of ~2.0 μm is P
Since it is necessary to completely remove the SG layer, even if the aluminum layer is exposed, the exposed surface is slightly etched.

By etching the aluminum layer, a beautiful aluminum background should theoretically be visible, but in reality, a colored portion that appears to be a foreign film is produced as shown in FIG. If such a colored portion occurs, the needle may not directly touch the aluminum layer in a later process, such as a die sorter process, resulting in poor contact.

Incidentally, it is thought that the reason why the colored portions are formed is that a large amount of aluminum ions generated by etching other aluminum layers due to overetching remain in the solution and are generated by gathering. Also, other contaminants,
That is, dirt on the wafer, objects spilled into the liquid from other patterns and bonding pads, and organic substances such as resist and organic agents are also considered to be involved, and these tend to occur frequently due to insufficient running water.

[Purpose of the invention]

In view of the above-mentioned conventional problems, the present invention improves the etching method for bonding pads of semiconductor devices.

[Summary of the invention]

In the method for etching bonding pads of semiconductor devices according to the present invention, prior to bonding a semiconductor device formed on a semiconductor device wafer to an aluminum bonding pad, the wafer is immersed in a solution for etching aluminum, and the wafer is immersed in the solution. It is characterized by etching by passing a weak direct current to prevent the formation of a foreign film on the bonding pad.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, which shows an etching apparatus used in one embodiment, parts that are the same as those in FIG. 3, which shows a conventional apparatus, are denoted by the same reference numerals as in the conventional apparatus, and a description thereof will be omitted.

The etching apparatus (1) shown in FIG.
Insert two electrodes (2a, 2b), with electrode (2a) made of platinum and electrode (2b) made of aluminum, as shown in Figure 5.
The electrode (2a) is connected to a weak DC power source with negative electrode (2b) and positive electrode (2b), and the current is applied once. Metal ions (+ charged) and impurity ions generated in the etching solution by this energization are attracted to the platinum electrode and neutralized.

The energization described above is just one example, but I have also experienced that reversing the applied potential is effective. There is also experience that alternating the potential was effective.

〔Effect of the invention〕

According to this invention, the problem that a foreign film is formed on the surface due to etching of an aluminum bonding pad, causing coloration in special parts can be completely solved. In addition,
This invention also has the advantage that it can be put into practice without requiring any major modifications to the apparatus.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an etching apparatus used in an embodiment of the present invention, FIG. 2 is a perspective view of a wafer carrier, and FIG.
The figure is a sectional view of a conventional etching apparatus, FIG. 4 is a top view based on a photograph showing an abnormality in a bonding pad, and FIG. 5 is an enlarged view of a part of FIG. 4. ↓ Etching device

Claims (1)

[Claims] A semiconductor characterized in that, prior to bonding a semiconductor element formed on a semiconductor wafer to an aluminum bonding pad, the wafer is immersed in a solution for etching aluminum, and the solution is etched by passing a weak direct current through the solution. Etching method for device bonding pads.