TiN: A Suitable Gate Material
Peter Singer, Editor-in-Chief
-- Semiconductor International, 9/1/2000
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Along with this move comes a need to switch the gate material from the doped polysilicon now used to a metal material due to the incompatability of silicon with high-k dielectrics during high-temperature anneals. One material under evaluation for use as a metal gate is titanium nitride (TiN), already commonly used as a barrier material.
Recent work at Motorola's Advanced Products Research and Development Lab (APRDL, Austin, Texas) examined electrical and physical properties of a physical vapor deposited (PVD) TiN gate metal on TiO2 and Ta2O5 gate dielectrics. The findings were somewhat inconclusive: although stacks of TiN/Ta2O5 could withstand temperatures as high as 850°C (800°C for TiN/TiO2) — temperatures normally encountered in typical processing — they showed excessively high leakage currents (more than 20 times higher) after high-temperature rapid thermal anneals of 1025°C. Researchers suspect this leakage may be due to an adverse TiN/dielectric interaction or process-induced damage. •
Research into Cu Electroplating Additives
It's clear the industry is beginning a transition from aluminum to copper, and the bulk of the copper will be deposited by electroplating. Although most are familiar with the basic ingredients of the copper electroplating solution, a well-kept secret is what additives are used. Common additives include leveling agents, brightening agents and surfactants, the combination of which can determine filling properties as well as the film's initial grain size and brightness or roughness.
The secret of a successful Cu electroplating solution is now revealed in a report out of Taiwan. Researchers there used an electroplating solution composed of CuSO4:5H2O, H2SO4, Cl ions, a leveling agent (a kind of ester with aromatic rings, with molecular weight < 1000 g/mol), a polyether (molecular weight < 4000 g/mol) as the surfactant and a small amount of silicone as a defoaming agent.
The electroplated films exhibited an excellent superfilling behavior (filling from the bottom up); 0.18 µm vias with an aspect ratio exceeding 5 were filled completely without any void or seam. The films were highly uniform and showed low resistivity, low porosity and a strong (111) texture. •
E-Diagnostics Program Unveiled
International SEMATECH issued guidelines for e-Diagnostics through its new program for remote diagnosis of semiconductor factory equipment. The guidelines target commercialization of open, Internet-based access for suppliers to monitor equipment. International SEMATECH's new Semiconductor Manufacturers Information Technology Security Council will participate by assuring Internet security within the e-Diagnostics program.
"The Internet is a revolutionary productivity enhancer, and International SEMATECH's e-Diagnostics program should keep suppliers and chip makers on track to take full advantage of the emerging capabilities of online diagnostics," said Michael Splinter, head of Intel's Technology and Manufacturing Group and International SEMATECH board member.
The guidelines, which emphasize worker safety and data security, also address the industry goal to cut by more than 60% the cost related to equipment maintenance and repair. Some of the key guideline components are:
•Open architecture based on mainstream computer technologies, non-proprietary standards and data models.
•An Internet-based approach that guarantees fab data is shared only with the appropriate supplier.
•Two-way communication between equipment and suppliers to enhance interactive problem-solving.
•E-Diagnostics for 200 and 300 mm wafer sizes.
•Data security to be assured, preventing the transmission of equipment data to chip or vendor competitors.
•Run-time data collection, storage and retrieval enabling data analysis and decision support capability.•Notifying the supplier when a tool is in need of routine preventive maintenance.
Future work of the e-Diagnostics program will include capturing best practices, compliance assessments, an implementation roadmap and more guideline revisions. The guidelines are available online.•
