<title>Fabrication of single/double crown-shaped capacitors on DRAM cell using phase-shift mask technology</title>

Abstract

Mostly, crown-shaped DRAM capacitor is formed by depositing a series of polysilicon and silicon oxide in a recess followed by etching back to form the vertical side-wall. In this paper, we are proposing a new method which is directly using crown-shaped photoresist pattern in conjunction with the chromless mask (or high transmission half-tone mask) to define the crown structure. A chromless 180 degrees phase shifters on transparent substrate (or high transmission half-tone phase shift mask) is used to create the 'destructive interference' between phase shifters and clear areas at the edges of the phase shifters to define 'dark areas' on the aerial image. The stacked capacitor pattern is defined as phase shifter region, therefore, the 'dark areas' on the edge of the phase shifter becomes the photoresist side-wall after exposing and developing. This crown-shaped resist side-wall then becomes the etching mask to form the crown-shaped capacitors. A special pattern layout of phase shift mask with two groups of phase shifters has been designed to form a double crown-shaped photoresist side- wall. The pattern includes the capacitor node phase shifter and a buffer shifter between two nodes. Lithography simulators, Depict-III, was used to simulate the aerial image intensity distribution of the phase shift mask layout. A single and double crown-shaped aerial image patterns have been simulated. The simulations have shown the results in agreement with the experiments, where a 0.15-0.25 micrometers wide vertical side-wall of a single crown pattern has been obtained. These new capacitors are estimated to increase the capacitance over the conventional thick capacitor by about 50 percent (for single crown) and 110 percent (for double crown).© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.