Applications of Ion Implantation Technology for Scaling Down Advanced Devices

To fabricate semiconductor devices, dopants are introduced into silicon to enable either n-type or p-type regions. Initially, diffusion-based doping methods were employed; however, they posed limitations in achieving precise control of dopant concentration profiles. Ion implantation is widely used as a method to form a surface or retrograde profile by controlling the ion energy to achieve a desired depth and controlling the integrated beam current to inject the desired dose. Consequently, it has become a widely adopted technique in semiconductor manufacturing. Although ion implantation was originally developed for doping purposes using only a few dopant species, its application has expanded significantly to using many non-dopant ions. These extended applications include pre-amorphization (PAI), modification of material properties, control of film stress, and enhancement of patterned structures. 

The PAI process destroys the periodicity of the silicon lattice, preventing ion channeling to improve shallow junction formation and transistor characteristics. It also reduces internal silicon defects by implant damage control. Also, amorphization can help metal silicidation. 

A second application is to harden or soften a deposited film by implanting ions into it, thereby making it suitable for subsequent processes such as etching, CMP, and deposition. 

A third application is to modify film volume using ions of significantly different size than the target film, which can be used to eliminate voids, improve adhesion, and reduce film stress. 

Finally, as pattern shrinkage becomes increasingly challenging, ion implantation is actively being used to improve post-exposure profiles, eliminate bridges that occur after patterning, and control contact hole size modulation.  

In this presentation, we introduce several case studies and recent experimental results related to diffusion barriers, film densification, adhesion enhancement, and pattern profile optimization. Ion implantation has proven to be a versatile technique not only for doping but also for engineering the properties of silicon and various thin films, thereby enabling new applications critical to advanced process scaling.