We report on the performance and reliability of our synchrotron radiation (SR) based x-ray lithography (XRL) system installed in Tanashi Works of Sumitomo Heavy Industries, Ltd. Our XRL facilities include a compact racetrack-type SR light source “AURORA-2S” (A2S), the injector microtron, a 3-m-long beamline, and the second version x-ray aligner. In 2000, A2S proved the beam lifetime of 16 h in regular operation at the designed beam current 500 mA. The XRL beamline offers a high-dose exposure rate of over 43 mW/cm2 on a wafer at beam current 500 mA. The x-ray aligner achieved an overlay accuracy better than 16 nm (3σ) using a video-based scattered-light alignment (SLA) system. In the SLA, edge scattering on matrix array patterns provides multispot video images for mask to wafer alignment. A 70 nm line and space (L/S) pattern was replicated with a gap of 15 μm. In resolution enhancement exposure, we replicated a 100 nm L/S and 1 100 nm hole pattern using a 200 nm L/S and a 200 nm hole pattern of x-ray mask, respectively.
We have developed a short beamline with high brightness for x-ray lithography. The beamline contains a single, a scanning toroidal mirror and a vacuum-protection system with an acoustic delay line. The practical exposure intensity on a wafer was approximately 50 mW/cm 2 at stored electron current of 500 mA. Dose uniformity of Ϯ2.8% was achieved in a 26 mmϫ26 mm exposure area by optimizing the scan speed. Minimum resolution of 80 nm was obtained with a 15 m gap. The optimum dose for TDUR-N908 ͑Tokyo Ohka͒ was 1300 mA s, which corresponds to exposure time of 2.6 s when the stored electron current is 500 mA. Since the sensitivity of TDUR-N908 is 110 mJ/cm 2 , the beam intensity in our beamline is estimated to be 43 mW/cm 2 . By reducing the exposure field, a beam intensity of more than 50 mW/cm 2 can be achieved.
Articles you may be interested inEfficient proximity effect correction method based on multivariate adaptive regression splines for grayscale ebeam lithography J. Vac. Sci. Technol. B 32, 031602 (2014); 10.1116/1.4875955 Performances by the electron optical system of low energy electron beam proximity projection lithography tool with a large scanning field J. Vac. Sci. Technol. B 23, 2754 (2005); 10.1116/1.2062435 Resolution-limiting factors in low-energy electron-beam proximity projection lithography: Mask, projection, and resist process J. Vac. Sci. Technol. B 22, 136 (2004); 10.1116/1.1635850 Resist debris formation and proximity exposure effect in electron beam lithography Low energy electron-beam proximity projection lithography: Discovery of a missing link We have proposed low energy electron-beam proximity projection lithography ͓T. Utsumi, Jpn. J.Appl. Phys., Part 1 38, 7046 ͑1999͒; J. Vac. Sci. Technol. B 17, 2897 ͑1999͔͒ ͑LEEPL͒ for LSI production lithographic processes below 100-nm-feature size. One and one half years ago, the proof of concept ͑POC͒ of LEEPL was successfully completed using an ␣ tool. Now, a  tool of LEEPL, which is similar to a mass production tool in the 100-and 70-nm-technology node, has been developed. We have already completed the performance evaluations of the  tool and confirmed proof of lithography. We obtained patterning resolution of 45-nm-L/S patterns and 48-nm -hole patterns in resist images and overlay accuracy of 23 nm ͑3͒ in the x direction and 31 nm ͑3͒ in the y direction over an effective area of 8 in. wafer. Furthermore, functionality of complementary mask alignment was demonstrated and logic type device-like patterns in 100-nm-technology node were fabricated.
Previously we described a video-based scattered-light alignment (SLA) system, capable of nanometer-scale alignment accuracy. In order to meet highly accurate alignment with low optical transparency in x-ray masks, we performed the modifications of alignment marks and an optical microscope imaging system on the conventional SLA system. The advanced SLA system has achieved a high alignment accuracy of 10.2–15.7 nm (|mean|+3σ) using a silicon carbide (SiC) x-ray mask of 18% optical transparency, coated with 5 nm thick chrome (Cr) film as an etching stop, with four different processed wafers: nitride, oxide, poly-Si, and aluminum. The different SiC membranes of 2–5 μm in thickness did not have an effect on the alignment accuracy in the nitride wafer.
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