Ranee Wai-Ling Kwong

Recent progress in electron-beam resists for advanced mask-making

Resists for advanced mask-making with high-voltage electron-beam writing tools have undergone dramatic changes over the last three decades. From PMMA and the other early chain-scission resists for micron dimensions to the aqueous-base-developable, dry-etchable chemically amplified systems being developed today, careful tuning of the chemistry and processing conditions of these resist systems has allowed the patterning of photomasks of increasing complexity containing increasingly finer features. Most recently, our research efforts have been focused on a low-activation-energy chemically amplified resist based on ketal-protected poly(hydroxystyrene). These ketal resist systems, or KRSs, have undergone a series of optimization and evaluation cycles in order to fine-tune their performance for advanced mask-fabrication applications using the 75-kV IBM EL4+ vector scan e-beam exposure system. The experiments have led to an optimized formulation, KRS-XE, that exhibits superior lithographic performance and has a high level of processing robustness. In addition, we describe advanced formulations of KRS-XE incorporating organometallic species, which have shown superior dry-etch resistance to novolak-based resists in the Cr etch process while maintaining excellent lithographic performance. Finally, current challenges facing the implementation of a chemically amplified resist in the photomask manufacturing process are outlined, along with current approaches being pursued to extend the capabilities of KRS technology.

New negative tone resists for subhalf micron lithography

Abstract New crosslinking type resist systems are described which use benzylic carbocation precursors carrying phenolic hydroxy group. The special feature of the new resists is the versatility of applications, ease of synthesis, high sensitivity, high contrast and a large process window. One such resist system has been used successfully in the back-end-of-the-line personalization for manufacturing advanced bipolar devices which required an exceptionally large process window. The new resist system is a promising candidate for surface imaging as well as for I-line, DUV and X-Ray applications.

New negative tone resists for sub-quarter micron lithography

A new acid amplified negative tone resist system is described which utilizes the formation of tetrahydropyranyl ether group for the crosslinking reaction. In a three component system, the phenolic groups of the matrix resin add to the dihydropyranyl groups of the crosslinker in the imaged areas. N-sulfonyloxy triflate or triphenyl sulfonium triflate are used as photoacid generators. The resist has excellent sensitivity to DUV, E-Beam, and X-Ray and is also used for positive tone surface imaging.

Improved underlayers for acid amplified resists

Abstract Acid amplified resists represent a major development in lithography in the last few years. It is recognized that for precise CD control with these resists in device manufacturing, it is required that the processing environment be free of any basic contaminants. Top coat protection of the resist films in conjunction with rigorous exclusion of basic chemical vapors in the work area has been recommended to minimize the effects of environmental contaminants. Another important variable in determining the resist performance is the effect of substrate chemistry which has received little attention in the literature. This paper provides an understanding of these effects and gives a general method to circunmvent the problem.