Plasma enhanced atomic layer deposition by means of an Anode Layer Ion Source for electronics packaging applications

Abstract

Since the successful introduction in the Western economic area of Atomic Layer Epitaxy (ALE) by Suntola's team [1] the technique more extensively known as Atomic Layer Deposition (ALD) has been slowly gaining acceptance in the field of thin film deposition [2]. There are many benefits of ALD, however, in terms of deposition rates and management of reactive gas species in complex 3D structures (such as Through Silicon Vias) there is still a long road ahead. In addition, typical ALD coatings require high temperature on substrates in order to promote surface chemical reaction between surface and incoming gas species. Sometimes a substrate temperature cycling is also required. These factors in turn produce stress on the deposited films. Some of the interesting 3D features of semiconductor devices could be very sensitive to processing conditions such as those involving ALD thermal cycles, for that reason Plasma Enhanced ALD (PEALD) techniques are of interest. PEALD has been introduced in order to lower the temperature requirements for the ALD process and also in order to control the properties of the ALD deposited film. The industrialization of such process presents a number of challenges. In PEALD, it is of interest to control the nature and degree of interaction of such plasmas with the surface chemistry. In novel wafer level electronic packaging technologies using TSVs that require high aspect ratio penetration plasmas could find difficult to penetrate so that effective chemical reaction is achieved. Standard deposition techniques show normally bad step coverage. A possible solution would be the use of medium energy ion beams in order to promote the chemical reactivity of the layering at deep trenches for example. For that reason, plasma sources which can control the energy of the ion beam are of special interest. One of those sources are the so called Anode Layer Ion Sources (ALIS), which can be extended in such a way that could cover very large areas. The results of the investigation and use of ALIS in PEALD depositions on silicon trenches will be presented.