AVS2009 Session PS+MS-MoA: Plasma Challenges at the 22nm Node and Beyond

At the 22nm technology node for logic devices many novel semiconductor technologies are being considered, each of which impacts etch process development and control. These technology performance challenges drive increases in carrier mobility (necessitating application of high strain liner and epi materials and reduction in silicon loss budget and gate height scaling), increased packing density (limiting resist trim budgets, increasing CD shrink requirements, and increasing integration of eDRAM), and achieving target resistance and capacitance (necessitating the introduction of porous low-k dielectrics and better profile control). The challenges introduced by these elements on dry etch processes, tooling, and controls is discussed in detail.

Widespread aggressive device scaling beyond lithographic limits require dry etch processes to provide controllable CD reduction to meet design groundrules. In particular, limited improvement in imaging at the 22nm node results in challenges in scaling on the plasma equipment. The implementation of multiple exposure techniques to achieve design rules for several key levels drives additional process control across multiple exposure and etch steps. Reduction in the available mask thickness required to preserve the lithography process window have driven the need for highly selective etch processes, generally at the expense of uniformity, defectivity, and profile of the transferred pattern. Later generation lithographic materials are expected to continue to exhibit increased sensitivity to line edge roughness, and drive additional implementation of novel masking materials. Process and tooling technology needs required to address these imaging challenges are discussed.

How we can overcome this situation? Some ideas will be presented highlighting the complexity of the situation and the need for close interaction of all involved parties.

Due to increased device integration complexity, there are significant challenges to technology scaling for Logic devices at 22nm and beyond. The issues range from difficulties in scaling device threshold voltage (V_t), and electron and ion mobility enhancements to achieving the proper leakage current for low power devices. Proposed solutions to overcome these challenges include adoption of Metal Gate High-k for threshold voltage and leakage current engineering, to various Strained Silicon techniques to enhance electron and ion mobility, and FinFETs for beyond 22nm technology node. In this presentation, we will review some of challenges associated with front-end logic integration schemes, such as control of Si Recess and Si damage. Si loss and damage after gate etch, spacer etch, and strained Si etch applications can impact source-drain junction depth, and increase device leakage. We will discuss various mechanisms for Si loss and damage, work done by previous authors, what is required at 22nm and beyond, implication for etch and post etch clean, and areas where better understanding is required.