by Debra Vogler, senior technical editor, Solid State Technology
January 25, 2010 – Novellus Systems next-generation ultra-violet thermal processing (UVTP) system, the SOLA xT, targets the manufacture of advanced logic devices at 45nm and below with a proprietary UVTP treatment process that modifies the physical characteristics of a previously-deposited film through exposure to ultraviolet light and heat. The new system has on-board UV monitoring and a customizable optics assembly and is designed to be extendible over multiple device generations. The first SOLA xT system will be shipped to UMC’s Fab 12i in Singapore.
A multi-station sequential processing (MSSP) architecture allows independent control of temperature, wavelength, and intensity at each station. The company reports obtaining UV-treated ultralow-k (ULK) films with a 25% greater hardness compared to single-wavelength, single-temperature curing solutions. According to Kevin Jennings, SVP of the company’s PECVD business unit, this feature enables the new system’s extendibility to future technology generations, where new materials are likely to be introduced.
By processing each wafer through a single wafer path, the tool’s architecture enables one statistical distribution of data compared to competitive solutions with up to four or six different wafer paths, and hence as many different statistical distributions, the company asserts. Simulated data showing the wafer-to-wafer performance using the SOLA vs. competing offerings (see figure below) was provided by Boaz Kenane, senior director of SOLA products at Novellus. (The effects illustrated are simulations of competitor WtW performance, seen in end-user results that cannot be shared publicly.) Among the challenges for the application, according to Kenane, is that the wafer-to-wafer performance can be impacted by the following: 1) For front-end-of-line films, the differences between chambers can cause differences in device speed performance and can result in these devices having to be binned separately; and 2) for ULK curing, depending on the UV cure performance, film hardness can be different — this could potentially affect packaging yield.
Wafer-to-wafer performance is also enabled by the MSSP treatment. As an example, explained Kenane, in porous ULK treatment, porogen removal and subsequent backbone strengthening are best done at different temperatures, wavelengths, and intensities. "In a SOLA chamber, each station can be configured with the substrate at a different temperature, different wavelength of radiation, and different intensity, if required/desired," he said. "All wafers pass through the same wafer path (i.e., all stations) and no transfer between chambers needs to be performed."
To achieve greater production efficiencies, the new system features on-board UV monitoring and advanced algorithms to maintain stable wafer-to-wafer performance. "UV curing performance is directly correlated to the performance of the UV source and the window through which UV is transmitted to the wafer," Kenane told SST. "The time-scale over which UV incident on the wafer changes due to the source is different from that due to changes/deposition on the window." Additionally, the change at each station of the four-station platform may be different, he explained, so the differences may be due to the particular process by which the porogen or other chemistry is removed from the wafer. "The advanced algorithm compensates for the number of wafers processed, as well as the film compensation and thickness," he said.