Yasushi Ohkubo

Development of attenuating PSM shifter for F2 and high-transmission ArF lithography

A new att-PSM shifter for both F2 and high-transmittance ArF lithography was developed. This shifter consists of SiON / TaHf in stacked layers. SiON for phase shift layer has a moderate transmittance and refractive index, and has sufficient laser durability. The TaHf film, which is a transmittance control layer, was effective as a functional layer in mask dry etching. Adopting the 3 step etching procedure, low damage of the quartz surface and less impact to CD shift was realized. It was confirmed that a new shifter has also sufficient feasibility to the mask inspection and repair process.

Development of new chrome blanks for 65-nm node and beyond

For advanced reticle fabrication, a resist thinning technique continues a promising trend of the resolution enhancement. To bring out thin resist performances, a new chrome absorber has been developed for the second layer of 193nm att-PSM. The new chrome absorber is thinner and has a higher dry-etch rate than our current products, such as NTAR5. This new chrome absorber can utilize a super thin resist application because of a reduction in dry-etching time. Additionally, a technique of film stress reduction was also developed to reduce placement shift by film stress relaxation. The new chrome absorber with super thin resist (TF blanks) exceeds current products in the mask-making metrics of resolution and CD performance. This performance will meet the requirements of 65nm-node and beyond.

Advanced binary film for 193nm lithography extension to sub-32-nm node

The proportion of mask fabrication in the total cost budget for IC production is increasing, particularly for the double patterning generation. Prolonging mask lifetime is very effective in reducing the total mask cost. The factors shortening the mask lifetime principally damage by cleaning and by 193nm excimer laser irradiation during wafer exposure. In order to solve these issues, Advanced Binary Film (ABF) was developed that is more durable against 193nm irradiation during wafer exposure, and has superior cleaning durability. We confirmed the dry etching characteristics of the ABF, using 100nm thick Chemically Amplified Resist and exposure by 50keV EB tool. We obtained impressive results from the ABF evaluation, through cycle cleaning tests (simulating cleaning during pellicle re-mounting), ArF irradiation damage and the effects on Critical Dimension changes.

Advanced NLD mask dry etching system for 90-nm node technology

Front-end semiconductor lithography demands smaller size of patterns for 90 nm node and beyond, on both Si wafers and photomasks. In dry etching for photomasks, it needs tighter CD uniformity and loading effect. For meeting these demands the advanced NLD (magnetic Neutral Loop Discharge) mask etcher has been developed, because it could operate at lower pressure for reducing loading effect than conventional ICP etchers, due to the magnetic confinement of electron in plasma generation. In the NLD mask etcher, the configuration of plasma source was investigated for better performance and the etching condition was re-optimized for improving selectivity. Consequently, the selectivity of Cr/resist (ZEP-7000) was more than 1.6, compared with 0.95 in the previous condition. And also, the CD uniformity in Cr etching was improved to meet our target 6 nm (3 sigma) around 0.68 Pa. However, in the view of reducing loading effect, other condition that is lower pressure than 0.68Pa and adding Helium (HE) showed smaller global loading. Therefore, making a balance of uniformity and loading is necessary to get better performance in mask process. We also propose a basic condition using the advanced NLD mask etcher for dry etching a MoSiON shifter of atenuated PSM in this paper.

CAR blanks performance for advanced reticle fabrication

DUV (Deep Ultra-Violet) laser reticle writers were released to the market for advanced reticle fabrication in 2002, AZ-DX1100P resist (for KrF lithography) has historically been employed for these tools. To respond to further high-end requirements, a new resist more friendly to DUV reticle fabrication is needed. FEP171 is a positive-type CAR (Chemically amplified resist) developed for EB reticle fabrication, which is sensitive to DUV as well. In this paper, we have investigated the applicability of FEP171-coated blanks for DUV reticle fabrication. As the results show, FEP171 could achieve 200 nm patterns by DUV exposure. FEP171 blanks showed superior performance in resolution and profile as compared to AZ-DX1100P. FEP171 blanks are promising for DUV reticle fabrication as well as EB reticle fabrication.

Multi-layer resist system for 45-nm-node and beyond: Part II

The CD requirements for the 45nm-node will become tighter so as it will be difficult to achieve with 65nm node technologies. In this paper, a method to improve resolution by using DRECE (Dry-etching Resistance Enhancement bottom-Coating for Eb) will be described. After all, DRECE has five times as high dry-etch resistance than the EB resist, and this enables to accept higher anisotropic dry etching condition. By optimizing dry etching conditions, the CD iso-dense bias dropped to 1/3 and the CD shift was reduced to 1/2. Also, there was no negative effect to CD uniformity. From these results, we propose the use of DRECE for the 45nm-node technology.

Improvement of NLD mask dry etching system for 100nm node technology

The advanced photomask dry etching system using neutral loop discharge (NLD) has been thought as a promising candidate for the next generation technology, because the NLD plasma has a capability to control the plasma distribution and density. In previous work, we improved CD uniformity for 130nm node technology using the neutral loop modulation etching technique. However, 100nm node lithography requires tighter specification, thus we set a target to achieve CD accuracy of 6nm (3 sigma) by improving CD uniformity and loading effect of the NLD dry etching system. First, we changed the system configuration: exhaust place, reactor size, and electrode shape. Especially, by optimizing the antenna configuration, we improved the unevenly distributed plasma. Additionally, we introduced a new etching technique to reduce CD shift from resist profiles by enhancing Cr/Resist sensitivity. Consequently, the NLD dry etching system for 100nm node technology was confirmed the effectiveness to improve CD performance using the above techniques.