Masao Ushida

Process development for EUV mask production

Absorber layer patterning process for low reflectivity tantalum boron nitride (LR-TaBN) absorber layer and chromium nitride (CrN) buffer layer were improved to satisfy high resolution pattern and high level critical dimension (CD) control. To make 100nm and smaller pattern size, under 300nm resist thickness was needed because of resist pattern collapse issue. We developed absorber layer dry etching process for 300nm thickness resist. Absorber layer patterning was done by a consequence of carbon fluoride gas process and chlorine gas process. We evaluated both gas processes and made clear each dry etching character. Sufficient resist selectivity, vertical side wall, good CD control and low buffer layer damage were obtained. Then, we evaluated how buffer layer dry etching affects EUV reflectivity. Finally, we evaluated EUV mask pattern defect inspection and defect repair. Sufficient contrast of mask pattern image and good repair result were obtained using DUV inspection tool and AFM nano-machining tool, respectively.

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.

The ultimate chrome absorber in photomask making

193nm-immersion lithography is the most promising technology for 32nm-node device fabrication. A new Cr absorber (TFC) for 193-nm attenuated phase-shift blanks was developed to meet the photomask requirements without any additional process step, such as hardmask etching. TFC was introduced with a design concept of the vertical profile for shorter etching time, the over etching time reduction. As a result, the dry-etching time was dramatically improved by more than 20% shorter than the conventional Cr absorber (TF11) without any process changes. We confirmed that 150nm-resist thickness was possible by TFC. The 32nm technology-node requirement is fully supported by TFC with thinner CAR, such as resolution and CD performance.

Development of halftone phase-shift blank and mask fabrication for ArF lithography

The halftone phase-shift mask has been in practical use for i-line and KrF lithography. In ArF lithography, the HtPSM is also considered to be a promising resolution enhancement technique for its simple structure and fabrication process required. We in HOYA have attempted to expand the applicability of our MoSi-based HtPSM blank technology to ArF lithography, helping extend the life of the existing infrastructure for conventional HtPSM fabrication. We have completed tuning our new MoSi-based film for ArF application. The films optical properties, chemical durability and ArF laser irradiation durability meet industry requirements; and it is compatible with conventional mask-making process and repair techniques for the KrF HtPSM.

Photomask blanks quality and functionality improvement challenges for the 130-nm node and beyond

Lithography will use various types of resolution enhancement technique on reticles such as EAPSM and OPC to extend refractive reduction optics to the 130 nm node and below. And there are mountainous difficulties that confront mask- makers as well as photomask blanks manufacturers now. In this paper, photomask blanks development status is introduced, and issues to be solved for the future are discussed.

Development of embedded attenuated phase-shifting mask (EAPSM) blanks for ArF lithography

The embedded attenuated phase-shift mask (EAPSM) has been in practical use for i-line and deep UV lithography. In 193 nm lithography, too, the EAPSM is considered to be a promising resolution enhancement technique for its simple structure and fabrication process required. We at HOYA have attempted to extend the applicability of MoSi-based EAPSM blanks to 193 nm lithography, helping extend the life of the existing infrastructure for conventional EAPSM fabrication. We have completed tuning our new MoSi-based film for 193 nm lithography and characterized its optical properties, chemical durability, ArF laser exposure durability and mask- making process compatibility.

HOYA deep-UV EAPSM blanks development status

Embedded attenuated phase-shift mask (EAPSM) is a feasible one as resolution enhancement technique (RET) for its simple structure and fabrication process. Several properties for the shifter film are required, such as adequate optical constants, a properly low transmittance at defect inspection wavelengths, chemical cleaning durability, DUV exposure durability naturally, as well as film pinhole and particle defect quality level. Several materials had been examined for EAPSM, and some of them are being practically utilized in the industry. We at HOYA also have been researching and developing an optimal material, and have been supplying MoSi-based EAPSM blanks for both i-line and deep UV application. This paper describes EAPSM blanks development history in the industry and the present status of HOYA deep UV EAPSM blanks functionality and quality as well as future improvement and development plan.

Development of deep-UV MoSi-based embedded phase-shifting mask (EPSM) blanks

Embedded phase-shift mask (EPSM) has an advantage in comparison with several other phase-shifting mask approaches because of its simple structure and fabrication process. We tried to modify MoSi-based EPSM blanks by re-examining the material and by optimizing sputtering condition in order to produce more useful EPSM blanks for Deep UV lithography technology. New MoSi-based EPSM blanks for which Nitrogen gas is used as the reactive sputtering gas has been developed. And it has been confirmed that the New MoSi-based EPSM (MoSi-N) blanks are superior to HOYA previously developed one (MoSi-ON) in chemical durability, manufacturing stability and Dry Etching property.

Evaluation of molybdenum silicide for use as a 193-nm phase-shifting absorber in photomask manufacturing

The introduction of 193-nm lithography is expected to provide a one-generation improvement in lithographic imaging capability. This will only happen if all of the enhancements presently being used for 248-nm lithography are also available at 193 nm. Attenuating phase shift materials have been developed by a few mask vendors for use at 193 nm. A molybdenum silicide phase shifting absorber has been developed by Hoya and evaluated by IBM and Hoya. Transmission and phase uniformity have been evaluated, and the contribution to these values from film thickness and etch variations have been identified. Plate-to-plate uniformity of phase and transmission have been measured. Durability of the film has been tested against 193-nm radiation exposure and chemical cleaning methods. Defect levels have been measured in the unprocessed film and the finished mask. The inspectability of masks made with this material has been evaluated on commercial inspection systems. The 193-nm molybdenum silicide film is compatible with etch and repair processes developed for 248-nm molybdenum silicide mask absorbers. The 193-nm molybdenum silicide film has a transmission of 6%, which is suitable for most attenuating phase shift applications. The film may be extendable to higher transmission values