The low energy electron beam proximity projection lithography (LEEPL) system consists of three properties: low energy electron beam, a parallel beam, and proximity projection. The low energy electrons increase the effective resist sensitivity and greatly minimize the proximity effect. Over a 20 µm depth of focus is achieved by the parallel beam on the proximity projection. The subdeflection system of the LEEPL system is useful in correcting the mask distortion and chip distortion on the wafer by a correction data map corresponding to the field, because of the space (>30 µm) between the wafer and the mask. The overlay accuracy of the machine itself is less than 14 nm and that of mix and match is less than 25 nm. This implies that the overlay between the LEEPL system and an ArF scanner in both the x and y directions are obtained. This machine shows the 48 nm CH resist patterns as the ultimate resolution. The cost of ownership (CoO) of the LEEPL system for a 65 nm node device will be approximately less than $25/wafer/layer and the value is lower than that of an ArF scanner.
Low Energy Beam Proximity Projection Lithography (LEEPL) has emerged as a lithographic production tool, named as LEEPL-3000, for a 60nm-node DRAM and MPU. The characteristics of this system are wide exposure field, highly-accurate overlay, deep depth of focus (DOF) and little proximity effect. A scanner or a stepper mono-field is able to be exposed by this system and maximum exposure filed size is 46mm x 46mm exclusively for two-or four-divided complementary masks. The acceleration voltage is 2kV and the exposed current varies up to 20μA. The critical dimension (CD) uniformity, including a mask-pattern deviation, is about 8nm as 3σ at 100-nm line and space patterns in 46mm x 46mm filed. A CD-dose margin for 60-nm isolated lines is over 12% and the focus margin is greater than 20μm. The accuracy (3σ) of machine-itself is less than 14nm and that of machine-to-machine is 20-25nm.
The image placement (IP) error correction is one of the advantages for E-beam lithography tool. LEEPL (Low Energy Electron beam Proximity-projection Lithography) 1,2) which is using stencil mask is able to shift the mask patter image by e-beam angle control. To use this unique technique week point of the stencil mask distortion is compensated. The flexibility of LEEPL E-beam IP correction for over lay is evaluated. The LEEPL E-beam IP correction is done by Sub-Deflector beam control. The feature to improve the over lay accuracy is introduced. It is not only for Mask IP error correction but also for Mask distortion by holding, under layer shot distortion and wafer chucking distortion.