Phase-width balanced alternating phase shift mask design

Abstract

A method is provided for designing an altPSM mask including a substrate. The method includes the following steps. Provide a circuit layout. Identify critical elements of the circuit layout. Provide a cutoff layout dimension. Identify critical segments of the circuit layout which are critical elements with a sub-cutoff dimension less than the cutoff dimension. Create basic phase shapes associated with the critical segments. Remove layout violations from the phase shapes. Determine whether the widths of phase shapes associated with a critical segment have unequal narrower and wider widths. If YES, then widen each narrower phase shape to match the width of wider phase shape associated with the critical segment and repeat the steps starting with removal of layout violations until the test answer is NO. When the test answer is NO, provide a layout pattern to an output.

Description

technical field [0001] The present invention relates to a lithography method applied in the design and manufacture of very large scale integrated circuits (VLSI), and more particularly to an improved method for forming a phase shift mask (Phase Shifted Mask) design. Background technique [0002] VLSI complementary metal-oxide-semiconductor (CMOS) chips are fabricated on silicon wafers through a series of process steps. These process steps include adding material to the wafer by utilizing addition processes such as low pressure chemical vapor deposition (LPCVD), sputtering operations, and the like. Other steps include removing material from the wafer using processes such as wet etching, reactive ion etching (RIE), and the like. In addition, the wafer can be further processed by material modification methods such as oxidation, ion implantation and similar steps. These physical and chemical operations affect the entire wafer. For example, if the wafer is placed in an acid ba...

AI Technical Summary

Problems solved by technology

[0047] However, Image 6 The results in reflect the obvious fact that the narrow outer phase line widths of the regions 12A / 12B at both sides of the embedded members VA / VB are very different in width compared to the very wide region 24

Because Image 6 The profile of the light wave intensity from left to right in is not uniform, so this imbalance of phase width at opposite sides of the embedded member VA / VB may cause process window degradation and may introduce pattern placement errors

[0048] Although merging phase domains may be limited, it cannot be completely avoided using techniques that produce phase transitions spanning narrow intervals between 180° phase domains

Thus, in view of the above discussion, it is necessary to provide a method of designing an alternating phase shift mask (altPSM) that minimizes the unbalanced phase width, which is caused by the building blocks, with an acceptable phase width difference. The component has embedded neighbors on only one side and causes process window degradation and image placement errors

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