Ching-Yu Chang

A 90-nm CMOS device technology with high-speed, general-purpose, and low-leakage transistors for system on chip applications

A leading edge 90nm bulk CMOS device technology is described in this paper. In this technology, multi Vt and multi gate oxide devices are offered to support low standby power (LP), general-purpose (G or ASIC), and high-speed (HS) system on chip (SoC) applications. High voltage I/O devices are supported using 70/spl Aring/, 50/spl Aring/, and 28/spl Aring/ gate oxide for 3.3V, 2.5V, and 1.5-1.8V interfaces, respectively. The backend architecture is based on nine levels of Cu interconnect with hot black diamond (HBD) low-k dielectric (k<=3.0).

Watermark defect formation and removal for immersion lithography

In immersion lithography, water drop residue has been identified as the source of watermark defects. Many methods have been studied to reduce water drops outside of the immersion area. However, from a physical point of view, the wafer surface is very hard to keep dry after immersion exposure. The water drop residues easily cause watermark defects that ranges from micrometer-size circular defects to sub-micron scum defects. In this paper we describe a few new methods to understand watermark formation. We also describe our studies on various water drop sizes and their impact on CD and defects. Our results show that major watermark defects occur as a result of the presence of relatively small water drops. A few methods have also been studied to reduce the impact of watermarks in order to remove watermark-induced pattern defects on wafers. These methods include post-immersion exposure treatment as well as novel material and process improvement methods. By applying these methods, we are able to remove watermark defects without an additional resist protection layer while still maintaining good resist lithographic performance.

Nanoscale inhomogeneity and photoacid generation dynamics in extreme ultraviolet resist materials

The development of extreme ultraviolet (EUV) lithography towards the 22 nm node and beyond depends critically on the availability of resist materials that meet stringent control requirements in resolution, line edge roughness, and sensitivity. However, the molecular mechanisms that govern the structure-function relationships in current EUV resist systems are not well understood. In particular, the nanoscale structures of the polymer base and the distributions of photoacid generators (PAGs) should play a critical roles in the performance of a resist system, yet currently available models for photochemical reactions in EUV resist systems are exclusively based on homogeneous bulk models that ignore molecular-level details of solid resist films. In this work, we investigate how microscopic molecular organizations in EUV resist affect photoacid generations in a bottom-up approach that describes structure-dependent electron-transfer dynamics in a solid film model. To this end, molecular dynamics simulations and stimulated annealing are used to obtain structures of a large simulation box containing poly(4-hydroxystyrene) (PHS) base polymers and triphenylsulfonium based PAGs. Our calculations reveal that ion-pair interactions govern the microscopic distributions of the polymer base and PAG molecules, resulting in a highly inhomogeneous system with nonuniform nanoscale chemical domains. Furthermore, the theoretical structures were used in combination of quantum chemical calculations and the Marcus theory to evaluate electron transfer rates between molecular sites, and then kinetic Monte Carlo simulations were carried out to model electron transfer dynamics with molecular structure details taken into consideration. As a result, the portion of thermalized electrons that are absorbed by the PAGs and the nanoscale spatial distribution of generated acids can be estimated. Our data reveal that the nanoscale inhomogeneous distributions of base polymers and PAGs strongly affect the electron transfer and the performance of the resist system. The implications to the performances of EUV resists and key engineering requirements for improved resist systems will also be discussed in this work. Our results shed light on the fundamental structure dependence of photoacid generation and the control of the nanoscale structures as well as base polymer-PAG interactions in EVU resist systems, and we expect these knowledge will be useful for the future development of improved EUV resist systems.

Directed Self-Assembly (DSA) for contact applications

Directed self-assembly (DSA) of block copolymers offers opportunities for resolution enhancement of existing patterning by pitch splitting, contact hole (CH) shrinks or, improvement of pattern profile or patterning window.1-2 By co-optimization of guiding pattern geometry, guiding pattern profile, block copolymer formulation, pattern transfer steps, the after-etch DSA patterns meet target pitch ratio. This DSA assessment shows combination of DSA and single iArF-patterning has potential to meet the specific CD dimension and pitch requirement of a conventional patterns that requires double-patterning.