SSL Seminar Series 2003 No.1

Combined talks (three speakers)

Date: May 9, 2003
Time: 5:00-6:00pm
Venue: Physics Resource Room (Blk S13 # 02-16)

Speaker I: Mr. Siddharth Joshi
Hydrophilic Surface Induced Nano-patterning of di-block Copolymers

In recent years, nano-patterned (NP) surfaces of polymers have become a subject of intense study in both experimental and theoretical physics. The vast technological applications of patterned surfaces in nano-circuits, nano-wires, sensors as well as biomedical tools have drawn enormous scientific attention. Parallel to this, we also embark on NP based research specifically on interactions between block copolymers (BC) and surface of a substrate that are governed by their physical and chemical properties. We would like to establish the surface characterization methodologies for NP organic surfaces. Firstly, we exploit surface sensitive spectroscopy tools such as Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and Surface Plasmon Resonance Spectroscopy (SPR) techniques. Importantly, we propose a new surface, Self Assembled Monolayer (SAM) of COOH-C15SH thiol/Au(111)/Mica to generate a patterned polymer layer. Formation of NP surface is based on surface induced nano-phase separation of di-block copolymers (DBC), poly styrene-block-2-polyvinylpyridine (PS-b-P2VP) and poly-styrene-block-4-polyvinylpyridine (PS-b-P4VP) as listed in Table 1(a). The intrinsic properties of the two blocks will eventually lead to a phase separation. In addition, different chemical affinity of each block with COOH-C15SH thiol adsorbed onto an Au(111)/Mica surface will also enhance the formation of nano-patterns. The di-block copolymers exhibited two types of surface-induced NP (worms and dot/islands) due to their different compositions of block's molecular weight. Table 1(b) lists the dimensions of these patterns on SAM of COOH-C15SH thiol/Au(111)/ mica.

Speaker II: Mr. Ab Razak Chanbasha
Ultra-low Energy Secondary Ion Mass Spectrometry

Downsizing in microelectronics has generated the need for ultra-shallow junctions (< 40nm). At this depth, however, it becomes difficult to provide accurate depth profile of the dopants, as the surface transient effects of SIMS coincides. Improved depth resolution is also necessary for better thin-film and interfacial profiling. These analysis are possible with ultra-low energy SIMS.
In this work, we will study the characteristics of ultra-low energy SIMS using O2+ and Cs+ ion beams at various incidence angles. Having understood this, we will attempt to optimize analytical techniques for accurate profiling and quantitation of B, As & SiON in Silicon.
In this presentation, we will highlight work done using O2+, below 1keV and at angles of incidence form 0o to 70o. Observations made on surface transient effects, sputter rates and depth resolution will be described.

Speaker III: Mr. Liu Rong
High Depth Resolution Secondary Ion Mass Spectrometry (SIMS)

Following the increasingly stringent requirements in the characterization of sub-micron IC devices, a good understanding of the various factors affecting ultra shallow depth profiling in secondary ion mass spectrometry (SIMS) has become crucial. Achieving high depth resolution (of the order of 1 nm) is critical in the semiconductor industry today, and various methods have been developed to optimize depth resolution.
In this work, we will discuss ultra shallow SIMS depth profiling using B and Ge delta-doped Si samples using low energy (e.g. 500 eV) O2+ primary beams. The relationship between depth resolution of the delta layers and surface topography measured by atomic force microscopy (AFM) is studied. The technique of oxygen flooding and sample rotation, used to suppress surface roughening is also investigated. The various factors that limit the depth resolution in ultra shallow SIMS depth profiling are discussed.