AES Analysis of Al Bond Pads in Electrically Insulating Surroundings Utilizing Metal Grid Contacting

TL;DR

This paper presents a method using metal grid contact to perform high-resolution AES analysis of aluminum bond pads beneath a polyimide layer, improving surface characterization for microelectronic device reliability.

Contribution

It introduces a novel sample preparation technique employing TEM grids to prevent charging during AES analysis of bond pads under insulating layers.

Findings

AES can effectively analyze bond pad surfaces with the new method.

The approach enables high spatial resolution surface characterization.

Sample charging issues are mitigated using metal grid contact.

Abstract

Bond pads are the electrical interconnections of a microelectronic device to the outside world. A polyimide layer (PI) on top of a microelectronic device protects the whole device against environmental impacts. The bond pads are accessible though openings in this electrically insulating layer. The oxide layer thickness and contaminations at the Al bond pad surface influence as well the quality of the mechanical and electrical joint between bond pad and bond wire as the durability of this interconnection. If a bond pad surface has to be analyzed with high spatial resolution Auger electron spectroscopy (AES) is the method of choice. AES utilizes an electron beam for excitation, which induces serious sample charging because of the PI layer. Sample charging can be avoided by metal grids, which are common in transmission electron microscopy (TEM) sample preparation. A TEM grid is pressed onto the sample while the bond pad of interest is centered in the square openings of the grid. Exemplarily analyses of bond pads demonstrate the applicability of this approach for AES measurements.