KLA-Tencor Re-engineers Wafer Inspection Tools
By David Lammers
KLA-Tencor said it has re-tooled its suite of wafer inspection tools, developing higher throughput and more capable systems for customers moving to the 2x node and beyond.
KLA-Tencor’s three production-level wafer inspection platforms are divided by the light source: the 2900 platform uses broadband, deep-UV light; the Puma 9650 employs a narrowband source, and the eS800 is an e-beam-based wafer inspection system with enough throughput for production-level inspection.
The 2900 system has been re-engineered from the ground up, said Tetsuya Yamamoto, senior product marketing manager. “The 2900 is a new platform that builds upon the 28xx. It is not a true extension — a lot of technology has gone into this new platform,” he said.
KLA-Tencor 2900 wafer inspection system. (Source: KLA-Tencor)
KLA-Tencor’s broadband tool uses a range of wavelengths, filtering the light source to the wavelength best suited to the job at hand. The re-engineered system offers the ability to find very small residues, protrusions and opens, as well as new defect types seen at the leading edge process nodes. The sensitivity is 3 times better than the previous generation platform, he said.
Rob Cappel, senior director of corporate marketing, said the 2900 system offers customers the ability to take design information and zero in on locations likely to provide problems, such as areas on the die using advanced reticle enhancement techniques (RETs). With those trouble spots fed into the system, customers can run high-sensitivity inspections. “They can go into the noise floor, do real-time binning and classification by designs and defects, including critical defect types,” he said.
The 2900 includes new brightfield and darkfield apertures, and wavelength bands that can boost the defect signal and reduce noise from the wafer. The platform improves defect detection and analysis, and supports a 12-bit dynamic range for defect capture in high-contrast areas such as memory transition regions. The image computer and stage were re-engineered to improve the defect location accuracy.
The Puma 9650 is an extension of the 9550, and customers can choose to upgrade existing 9550 platforms or buy new 9650’s. The Puma 9650 is a macro inspection system, targeted at larger defects in the range of 5 to 100 µm. Customers use the Puma systems to monitor for excursions in etch, CMP, and other layers. The Puma 9650 uses the same 355nm wavelength source, but offers improved noise suppression and smaller pixel sizes to collect information, said Jay Sorochin, director of marketing in the wafer inspection division.
Customers can choose to increase the sensitivity, or opt to inspect more wafers per hour, achieving higher throughputs. Cappel said some processes have a lot of wafer-to-wafer variation, and customers may have to sample more wafers in a specific lot, perhaps eight wafers, to catch that particular variability.
“Customers are pushing for more flexibility: increased sensitivity if they need it for a specific layer, or more throughput to capture wafer-to-wafer variability,” Cappel said.
The Puma 9650 also is able to suppress interference from repeating patterns in page break and transition regions, and has an extended dynamic range to improve the system’s response near array edges and in the periphery regions.
Kumar Raja, senior product marketing manager in the e-beam division, said the eS800 platform offers an improved ability to collimate and focus the e-beam. “The biggest challenge in e-beam inspection is to use the electrostatic and magnetic fields to build a better column,” he explained.
At one time, e-beam inspection systems were largely used for in the development and debug phases of new process development. More recently, semiconductor companies have asked for e-beam inspection tools with higher throughputs which can be used on the fab floor.
To accomplish that, KLA-Tencor developed new optics and better control of the landing energy from the electron gun, optimizing the surface conditions as the electrons interact with the surface of the wafer.
Cappel said the eS800’s electron gun and optics have the flexibility to adapt to various conditions which can affect the tool’s operating range. Also, the optical and e-beam development teams worked together to transfer algorithms from the optical to the e-beam division, as well as developing e-beam-specific algorithms within the e-beam group, which improve the signal to noise ratio.
The result is an e-beam inspection system with the sensitivity to find defects inside high aspect-ratio structures, as well as less conductive layers such as low-k dielectrics, and under-etch defects.
The semiconductor industry now faces a staggering array of technology transitions – including EUV and double patterning lithography, new materials, and 3D transistor structures — which require new wafer inspection systems, Cappel said.
“When we look back over history, over the next five to seven years the industry faces as much disruptive technology as we’ve seen in the history of the semiconductor industry. The closest thing we’ve seen to now was in the 2002 to 2005 period, when companies introduced dramatic design rule shrinks, there was a change in the wafer size, litho went to 193nm, and interconnects went from aluminum to copper,” he said.
Tags: KLA-Tencor, semiconductor manufacturing, wafer inspection