CD error budget of CP exposure

Abstract

We evaluate the projection fidelity of the Cell Projection (CP) using the Multi column cell (MCC) proof of concept (POC) tool [1][2][3][4][5][6]. The CP technology is originally developed as a method for reducing the shot counts of E-beam lithography systems. However, the higher repeatability of the shape is expected because the fixed size CP mask openings are used for each pattern. In the process of writing patterns by E-beam, the pattern deformation is inevitable due to the beam blur, proximity effect, and beam shaping error. If the model of beam deformation is established, the correction for the pattern deformation by modifications of CP mask opening shape can be carried out instead of additional shots. As a result, the shot count will be reduced.In this paper, we focused on Corner Rounding (CR) and Line End Shortening (LES) as two-dimensional properties of pattern deformation. Two-dimensional deformation should be decomposed in two components. One is the deformation in the process of CP mask manufacturing, and another is the deformation in the exposure process by e-beam writer tool. CP mask has been manufactured, measured and analyzed by Toppan printing. And using the CP mask, the exposure process error is measured by Advantest. By comparing the results, we evaluate the net amount of CP deformation caused in exposure process. Finally we confirmed the two-dimensional deformation is predictable by blur length that is obtained by one-dimensional CD-dose curve analysis.Keywords: electron beam exposure system, character projection(CP), corner rounding(CR), line end shortening(LES), membrane mask, resolution. INTORODUCTIONThe MCC-POC tool was built for evaluation of the adequacy of the parallel exposure concept by multi column architecture. Each column cell (CC) of the tool has a capability of CP exposure. Using a CP technology, the high pattern repeatability is obtained because the same designed patterns are exposed by specified CP openings for each design. In addition, the CP projection indicates higher resolution capability because the CP optics has one object plane to one image plane, while VSB has two object planes. Figure 1 shows the optical system of a CC. CP optics is almost free from the blur caused in the part of optical system between the first shaping aperture and the second shaping aperture of the VSB system.Recently, the pattern shape required to lithography becomes more complex for various correction techniques. As a result, shot count becomes very large in the case of rectangular pattern fracturing for VSB method. On the other hand, CP technology has the advantage that the shot shape correction can be achieved without shot count increase because the CP technology allows various correction methods, e.g. additional serif patterns build in a CP pattern together or changing the shape of the CP pattern opening itself.For carrying out such corrections, we should clarify the fidelity of projected pattern shape not only in one-dimensional but also in two-dimensional. One-dimensional property such as line wi...