Curvilinear mask handling in OPC flow

Abstract

The edge-based OPC has been serving the industry for more than 20 years with few changes in the way to alter the mask. In the past 10 years, ILT pioneers in the creation of the curvilinear mask using alternate algorithms. The two approaches differ so much that the experiences in conventional OPC do not easily translate to the use of ILT and vice versa. In this paper, we report a new system for curvilinear OPC built on top of the conventional OPC workflow without being limited to moving edges. It creates and manipulates the curvilinear shapes by generalizing the edge-based OPC to vertices. Conventional OPC techniques, including dissection, classification, target point placement, etc., keep playing central roles. Full-chip correction results demonstrate the good performance of the curvilinear mask for both contact and line/space patterns. The runtime cost of adoption is reported.

B-spline and Bézier curvilinear representations: a comparative discussion

“…As shown in Figure 9, the influence of a given control point is overlapping with those of its neighbors. This way, the curve is naturally smooth 4 .…”

“…Regarding the runtime, the inverse lithography models would take a long time for producing a satisfying solution. Currently, advances in algorithms, such as AI (Artificial Intelligence), as well as on computing power with latest CPUs and GPUs, have mitigated this issue [2][3] [4]. The second limiting factor was the mask writing time.…”

Curvilinear mask metrology: what is the equivalent critical dimension?

“…20,21 The second barrier-full-chip ILT-has also been removed, by applying GPU acceleration and a stitchless full-chip approach. 22,23 1.3 Multi-Beam Mask Writer Enables Curvilinear Masks The mainstream mask writer, the variable shaped beam (VSB) mask writer, for the leading semiconductor manufacturing was invented to write Manhattan patterns. It writes masks using a single beam that can produce a rectangular shot and 45-degree triangle shot with variable dimensions.…”

“…A Bezier curve is a parametric curve used in computer graphics and related fields. A set of discrete "control points" defines a smooth, continuous curve by means of a formula, 23 as shown in Fig. 5.…”

“…5. Instead of moving the sampling point in the segment OPC, control points are moved in the curvilinear OPC 23 (Fig. 6).…”