Toshimasa Shimoda

High-precision wafer-level Cu-Cu bonding for 3DICs

A high-precision Cu-Cu bonding system for three-dimensional integrated circuits (3DICs) fabrication adopting a new precision alignment methodology is proposed. A new pressure profile control system is applied in the thermocompression bonding process. Experimental results show that the alignment capability is 250 nm or better, with similar overlay accuracy (|average| + 3σ) for permanent bonding. These developments are expected to contribute to the fabrication of future 3DICs.

Full-field exposure performance of electron projection lithography tool

Electron projection lithography (EPL) is a realistic technology for the 65nm node and below, as a complementary technology of optical lithography especially for contacts and gate layers because of its high resolution and large process margin. Nikon has developed an EPL exposure tool as an electron-beam (EB) stepper and the first generation EB stepper; NSR-EB1A is now almost completed as an R&D tool for the 65nm technology node. Using a ϕ200mm reticle, a 20mm×25mm exposure field is realized. Full-field exposure performance of NSR-EB1A is shown. A 70nm isolated line and 1:1 nested lines are simultaneously resolved, as are 50nm 1:2 nested lines. 60nm contact holes are resolved with a depth of focus over a 10μm range and dosage window over ±6%. Stitching accuracy is about 20nm (3σ) and the single machine overlay is about 30nm (mean + 3σ). These data mean sufficient performance for device manufacturing of the 65nm technology node. The concept of a large subfield is one candidate for resolution and throughput e...

First dynamic exposure results from an electron projection lithography tool

Electron projection lithography (EPL) is one of the promising technologies below the 65 nm node, especially for contact hole and gate layers. Nikon is developing an EPL exposure tool as an electron beam (EB) stepper and the first generation EB stepper is now being manufactured. The voltage of 100 kV is adopted for electron beam acceleration. The subfield size is 0.25 mm×0.25 mm on the wafer and the deflection width of the electron beam is 5 mm on the wafer. The magnification of the projection optics is 1/4. A 5 mm×25 mm area from the φ200 mm reticle can be exposed by the combination of beam deflection and stage scanning motion (dynamic exposure). This area is called “a mechanical stripe.” After one mechanical stripe exposure, the reticle and wafer stages turn around and the next exposure of the adjacent mechanical stripe starts as a scan and stitch stage motion. Finally, a 20 mm×25 mm exposure field from the φ200 mm reticle is exposed. We report the first dynamic exposure in the history of EPL although on...

Nikon EB stepper: its system design and preliminary performance

Electron Projection Lithography (EPL) has a high potential for applicability beyond the ITRS 65 nm node, especially for contacts and gate layers. The concept of synchronization control of the Nikon EB stepper is explained. The reticle stage and the wafer stage are servo controlled to target positions individually. The residual stage position errors are compensated by the electron beam deflection control. The electron beam deflection is feed forward controlled using predicted stage position data from a subsystem called “Filter/Predictor”. The performance of the stage position prediction of the Filter/Predictor is described. This paper also reports the performance of the first EB stepper tool, the NSR-EB1A, during its preliminary adjustment phase. Dynamic scanning and stitching exposure, which requires synchronization of both the beam deflection motion and the stage scanning motion, was realized. Dynamic resolution of 100 nm and dynamic subfield stitching accuracy of 25 nm (3sigma) were obtained, and further improvement is expected.

High-Precision Wafer-Level Cu–Cu Bonding for 3-DICs

A high-precision Cu-Cu bonding system for 3-D ICs (3-DICs) fabrication adopting a new precision alignment methodology is proposed. A new pressure profile control system is applied in the thermocompression bonding process. Experimental results show that the alignment capability is 250 nm or better, with similar overlay accuracy (|average| + 3σ) for permanent bonding. These developments are expected to contribute to the fabrication of future 3-DICs.

Nikon EPL tool: the latest development status and results

Electron Projection Lithography (EPL) is considered one of promising technologies below 45nm node, especially for contact/via holes and gate layers. EPL has some nice features such as very high resolution to be applied for two device nodes, large process margin associated with large depth of focus and an expected lower CoO. Nikon has been developing an EPL tool, so-called EB Stepper. NSR-EB1A is the first EB Stepper that was designed as R&D tool for 65nm technology node and that was already delivered for Selete (Semiconductor Leading Edge Technologies, Inc.) at Tsukuba in Japan. Nikon has developed two NSR-EB1A tools so far, one system for Selete as a 300mm wafer system and the other for Nikons development and evaluation as a 200mm wafer system. Both tools have already started to show full performance data and good stability characteristics. The latest EB1A tool performance shows very good results in such data as the resolution of 50nm 2:1 L/S and 60nm 1:1 dense contact holes patterns, stitching accuracy of around 18nm, and overlay accuracy of around 20nm(X+3sigma).