Plant microRNAs (miRNAs) act as negative regulators of gene expression by slicing target transcripts or inhibiting translation. A number of miRNAs play important roles in development. In order to investigate the potential function of miRNAs during male gametogenesis in rice, we obtained both gene and small RNA expression profiles by combining microarray and high-throughput sequencing technologies. From the microarray datasets, 2,925 male gametophyte-specific genes were identified, including 107 transcription factors and three significant Argonaute genes (AGO12, AGO13, and AGO17). From the sRNA-Seq datasets, 104 unique miRNAs (miRus) were identified, including 47 known miRus and 57 novel miRus; interestingly, most of the new miRus are pollen-specific and not conserved among species. Furthermore, an interactive network of miRNA-target was constructed based on the two datasets. By employing enrichment analysis, the miRNA-regulated targets were found to be involved in both the up and down pathways, but predominantly in the down pathways, including 37 GO biological processes and 32 KEGG pathways. These findings indicate that miRNAs play a broad regulatory role during male gametophyte development in rice.

In the past few years, industry has made significant progress to deliver a stable high power EUV scanner and a 100 W light source is now being tested on the manufacuring scale. The success of a high power EUV source demands a fast and high resolution EUV resist. However, chemcially amplied resists encounter unprecedented challenges beyond the 22 nm node due to resolution, roughness and sensitivity tradeoffs. Unless novel solutions for EUV resists are proposed and further optimzed, breakthroughs can hardly be achieved. Oxide nanoparticle EUV (ONE) resists stablized by organic ligands were originally proposed by Ober et al. Recently this work attracts more and more attention due to its extraordinanry EUV sensitivity. This new class of photoresist utilizes ligand cleavage with a ligand exchange mechanism to switch its solubilty for dual-tone patterning. Therefore, ligand selection of the nanoparticles is extremely important to its EUV performance.

The introduction of EUV lithography to manufacturing requires the development of both new EUV exposure tools and photoresists. The main challenges for photoresists are to achieve high resolution, and low roughness patterning at very high sensitivity given the limited intensity of current sources. A new class of photoresist formed from ligand-stabilized metal oxide nanoparticles shows extraordinary sensitivity for EUV lithography. These nanoparticles are processed in traditional organic solvents for both deposition and development as negative tone resist; positive tone images are possible if the aqueous base developer is used in addition to a post-exposure bake step. This paper presents new developments in the study of ligand-stabilized nanoparticle photoresists for EUV lithography. It is our current understanding that a key aspect of the solubility change of these photoresists during exposure involves ligand displacement by anions generated from photoactive compounds such as sulfonic acid photoacid generators. Both positive and negative tone patterning are possible and depend on thermal treatment history and choice of developer. On the basis of a non-chemically amplified ligand exchange mechanism, new resist structures were created. Both aromatic and aliphatic carboxylic acids with different functional groups have been studied in the formation of the nanoparticles and include dimethylacrylic acid, isobutyric acid, toluic acid. It has been shown that those nanoparticles with higher binding affinity ligands show better resolution and line edge roughness under EUV exposure. Some formulations demonstrate EUV sensitivity as high as 1.4 mJ/cm 2 , while other formulations demonstrate that improved LER values of 3-5nm. The overall resolution, sensitivity and roughness tradeoff has been evaluated and provides an understanding of structure -property relationships. In this paper, we also discuss major efforts on the further understanding of the patterning mechanism. By testing the dissolution rate and plotting it in Hansen interaction triangles, we can compare the differences between different formulations and choose a suitable developer for each formulation. We also used the dissolution rate study to confirm the important role of PAG and ligand exchange for pattern formation. In addition, aspects of the EHS properties of these new photoresists have been investigated and will be discussed.

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