Yoshihisa Oae

Evaluation of Throughput Improvement by MCC and CP in Multicolumn E-beam Exposure System

In the Mask D2I project at ASET, the authors evaluated an e-beam multi column cell exposure system with character projection to expose photomask patterns of hp65nm and hp45nm devices. They prepared more than 2,000 characters in a deflection area of a character projection mask extracted from the hp65nm pattern. The character projection in the multi column cell system could expose patterns equivalent to those by the conventional variable shaped beams. In a typical pattern layout of photomasks for hp45nm devices, the four column cell system required an exposure time of about 1/3 of the time required by a single column system. The character projection can reduce the exposure time corresponding to the reduction of shot counts.

`NOWEL-2' Variable-Shaped Electron Beam Lithography System for 0.1 µm Patterns with Refocusing and Eddy Current Compensation

We have developed a variable-shaped electron beam (EB) lithography system which we call NOWEL-2. The system has the following features: (1) a short objective lens and a four-stage major deflection system; the landing angle at the corner of the 1.6 mm square major field is less than 2 mrad, and patterns from 0.1 to 3.0 µm are well resolved over the whole deflection field, (2) 20-bit digital-to-analog converter and high-precision current output amplifier, in which the least significant bit (LSB) corresponds to 0.0025 µm; linearity error is less than 1/4 LSB at 23±5°C, (3) refocusing and refocus-flyback; the edge sharpness of a 3 µm square beam was improved from 0.5 µm to 0.25 µm, (4) eddy current compensation; for a 100 µm electromagnetic jump, the waiting time is less than 50 µs, (5) continuously moving stage mode exposure; beam position accuracy is about 0.05 µm (3σ).

Accuracy of exposure during continuous stage movement in a variable shaped vector scanning EB lithography system

Abstract We have developed a variable shaped electron beam lithography system “NOWEL-2” [1,2]. Continuously moving stage exposure mode, which we call CM exposure mode, is used in the system. To achieve high butting and overlay accuracy in CM exposure mode, we measured the beam positioning error using the continuously moving mark detection method. Up to a stage velocity of 10 mm/sec, beam positioning error caused by eddy current and system vibration was less than 0.04 μm. Total beam positioning drift during exposure was decreased to about 0.08 μm by keeping the temperature of the electromagnetic deflectors and lenses constant.

Evaluation of throughput improvement and character projection in multi-column-cell E-beam exposure system

In the Mask D2I project at ASET, the authors evaluated an e-beam multi column cell exposure system with character projection to expose photomask patterns of 65nm and 45nm node logic devices with OPC corrections. They prepared more than 2,000 characters in a deflection area of a character projection mask extracted from the 65nm node logic device pattern. The character projection in the multi column cell system could expose patterns equivalent to those by the conventional variable shaped beams. In a typical pattern layout of photomasks of 45nm node logic devices, the four column cell system required the exposure time of about 1/3 of the time required by a single column system. The character projection could reduce the exposure time corresponding to the reduction of shot counts. The pattern priorities also reduced the exposure time as the result of shot count reduction and minimizing wait time for deflection settling.