The control of pattern defects is the most critical issue for the production of high-end photomasks with decreasing feature size and increasing mask complexity. Historically and in recent years, three options for photomask repair have been available: Focused Ion Beam (FIB), Laser and Electron Beam mask repair equipment. While each technique has its advantages and unique capabilities, each technology has suffered from a variety of accuracy, imaging and production reliability limitations.
Since 2001, the fourth mask repair method, nanomachining, has become the industry leader. The nanomachining technique is an extremely accurate method for subtractive removal of opaque mask defects utilizing the advantages of atomic force microscopy (AFM) for unrivaled imaging, edge placement and z-depth repair control. The Bruker nm-VI® photomask repair system represents the sixth generation of this high precision nanomachining technique.
Nanomachining is a unique defect repair technique in the semiconductor industry, combining the positional control of an AFM and proprietary Nanomachining hardware and software to perform material removal at nanometer levels.
The benefits of Nanomachining technology as applied to photomask repair are the precise and accurate removal of defects in Chrome, MoSi, OMOG, Quartz, EUV and various other exotic materials. Bruker's emphasis has been on materials that provide significant challenges for the current industry standard repair techniques; specifically, quartz bumps on alternating phase shift masks, trimming of carbon patches, multi-level materials, foreign materials, persistent unknown particles and precision repairs within tight lines and spaces.
The Nanomachining Advantage
Several advantages of the Nanomachining technique include the ability to:
- Machine in tight geometries with very high precision Z control
- Approximate line edge slope for both wet and dry etched material
- Image with resolution exceeding today’s needs
- Extend to future mask sizes and technologies including EUV
- Develop custom repair processes and tips quickly
- Image and repair quartz bumps of nearly any size and shape
- Minimize surface damage and achieve superior edge control and transmission