CD and IP accuracy in electron beam character projection technology

CD and IP accuracy in electron beam (EB) character projection (CP) was examined. We measured around 1 nm as critical dimension (CD) 3 sigma of CP line patterns without major and minor deflection. In the case of VSB, the values exceed 2 nm. This gap is based on the difference in the beam formation method of CP and VSB. Root of the difference of these two squares of 3 sigma are from 1.69 to 2.53 nm and it is caused by variation of relative position between beam and CP mask aperture in using VSB. We measured 1.64 nm as CD 3 sigma of CP line patterns with major deflection within 1520 × 680 μm and minor deflection within 80 × 80 μm and analyzed the data into local factor: 1.38 nm, major deflection factor: 0.72 nm and minor deflection factor: 0.51 nm. It seemed that CP technology for CD accuracy had sufficient potential to 45 nm half-pitch system. Then we also measured image placement (IP) accuracy of CP (position, gain and rotation of CP as to changing deflection distance for CP selection, area of CP aperture and major and minor deflection distance). The variation in the position to CP selection was observed and is considered to be due to electric or mechanical vibration of system. For our future 45 nm half-pitch system, we plan to raise the performance of each unit and to lower this variation. The dependence to change of the parameter of the system was also observed: (A) change of the rotation to CP selection deflection distance, (B) change of gain and rotation to CP area and (C) change of gain and rotation to major and minor deflection distance. We could compensate by using biased mask for (A) and (B). We are going to cope with (C) by narrowing major deflection distance.