ABSTRACT
The heavier mass of the Ga ions is found to cause impact-induced damage while carrying out circuit modifications on prototype chips [1]. The nondestructive secondary ion imaging of a surface is possible only with light ions [5]. In FIB systems, contamination is inevitable due to the use of liquid-metal ions, so an inert gas ion source is very much desired. For example, when LMIS is used for sputtering of copper, a Cu3 Ga phase alloy can be formed, which is particularly resistant to milling and contributes to the uneven profile [6]. Ga ions not only change the electrical properties but also can affect the magnetic properties of the devices. Ga staining due to deposition of Ga ions in the quartz substrate during FIB repair of a photomask is another important issue that limits the use of LMIS-based FIB systems. It has been demonstrated that when a Ga ion beam is used for photomask repair, implanted Ga ions can absorb 73% of incident 248 and 193 nm ultraviolet light, but only 0.7% of the incident light is absorbed when krypton ion beam is used for mask repair [7]. In direct deposition of insulator or metallic material using an FIB system, with the aid of a certain precursor gas, organic contaminants as well as Ga atoms are found to be included in the deposited film [8].
