Recently, in order to increase the number of transistors in wafer by small feature size, optical lithography has
been changed to low wavelength from 365nm to 193nm and high NA of 0.93. And further wavelength is aggressively
shifting to 13.5nm for more small feature size, i.e., Extreme Ultra Violet Lithography(EUVL), a kind of Next Generation
Lithography(NGL)1. And other technologies are developed such as water immersion(193nm) and photo resist Double
Patterning(DP). Immersion lens system has high NA up to 1.3 due to high n of water(n=1.44 at 193nm), the parameter k1
is process constant, but 0.25 is a tough limit at a equal line and space, if we use immersion lens with 193nm wavelength
than limit of resolution is 37nm. Especially, Double Exposure Technique(DET) process is widely studied because of the
resolution enhancement ability using a same material and machine, despite of process complication. And SADP(Self
Aligned Double Patten) is newly researched for overlay and LER(Line Edge Roughness) enhancement.
In this paper, we illustrate the feasibility of the shift double pattern for 65nm-node flash using a 193nm light
dipole source and the possibility of decrease minimum feature size using a property of silicon shrinkage during thermal
ArF Immersion lithography is the most promising technology for 45nm node and possibly beyond. However, serious
issues in ArF immersion lithography for semiconductor mass production still exist. One of the issues is immersion
specific defects, which are caused by photoresist component leaching and residual water droplets. In order to minimize
immersion specific defects, preventing water penetration into the resist film is regarded as an important factor. Several
research groups have reported that higher receding contact angle reduced defectivity. High receding contact angle of
film surface prevent water penetration into the resist film due to the hydrophobic nature. Resist component leaching
phenomenon also can be caused by the water penetration into the film, so hydrophobic resist can reduce leaching
In this paper, to investigate chemical leaching from resist surface, we evaluated the leaching value of PAG anion and
contact angles of various polymers according to their hydrophobicity. Hydrophilicity of a polymer was changed by the
degree of hydrophobic group substitution to polymer chain. We measured receding contact angle with four different
resists composed of water-repellent functiona group. Receding contact angle of resist surface increased as the portion of
water-repellent functional group increased. Also, the leaching amount of PAG anion decreased as the receding contact
angle of film surface increased. We expect that higher receding contact angle prevents chemical leaching from resist film
by repelling water at the surface. We will report detailed results in this paper.
Post exposure bake temperature sensitivity (PEB sensitivity) becomes important as the pattern pitch size shrinks gradually. There are several factors affecting the PEB sensitivity including acidity and diffusion of photogenerated acid, activation energy for deprotection reaction, free volume of base polymer, and so on. Our works were conducted as a part of the basic study for searching influential parameter of PEB sensitivity. We found that PEB sensitivity relies largely on not only acid diffusion parameter, but also the hydrophilicity of base polymer and protection group ratio. Also, we observed that bulkiness of deprotection group has great influence on PEB sensitivity. Detailed results will be reported in this paper.
As the device design rule is continuously shrinking, line end shortening (LES) has grown to be one of the critical problems in 193 nm photolithography. Among several factors causing LES, diffusivity of photo-generated acid seems to have the most profound effect. Also, diffusivity of base quencher produces equivalent effects on LES, but in the reversed way. Besides, post-exposure bake (PEB) condition is another key factor by affecting diffusion length of photo-generated acid. Low LES can be achieved by lowering PEB temperature or shortening its time. In this paper, we will discuss our experimental results to assess the determining factors of LES and suggest controllability of LES in ArF lithographic process.
The paper presented a new thermally expanded core(TEC) lensed fiber using a standard single-mode fiber(SMF), which was fabricated with a lens at fiber tip using mechanical polishing after expanding the core diameter of a single-mode fiber into about 20μm. This TEC lensed fiber shows that it has the working distance of 60μm and high coupling efficiency (>75%).