Root Cause Analysis and Correction of Single Metal Contact Open-Induced Scan Chain Failure in 90nm node VLSI

TL;DR

This paper presents a novel method for localizing and diagnosing open metal contact failures in 90nm VLSI using EBAC and EDX techniques, identifying incomplete resist removal as the cause and proposing an effective cleaning solution.

Contribution

First application of EBAC and EDX for diagnosing open contact failures in 90nm VLSI, with a proposed cleaning process to improve yield.

Findings

EBAC and EDX effectively locate open contact failures.

Incomplete resist removal causes the failures.

Diluted HF cleaning improves manufacturing yield.

Abstract

In this paper, the localization of open metal contact for 90nm node SOC is reported based on Electron Beam Absorbed Current (EBAC) technique and scan diagnosis for the first time. According to the detected excess carbon, silicon and oxygen signals obtained from X-ray energy dispersive spectroscopy (EDX), the failure was deemed to be caused by the incomplete removal of silicate photoresist polymer formed during the O2 plasma dry clean before copper plating. Based on this, we proposed to replace the dry clean with diluted HF clean prior to the copper plating, which can significantly remove the silicate polymers and increase the yield.