Study on the Distribution Control of Etching Rate and Critical Dimensions in Microwave Electron Cyclotron Resonance Plasmas for the Next Generation 450 mm Wafer Processing

Abstract

A newly designed microwave electron cyclotron resonance (ECR) plasma etching reactor has been developed for 450 mm wafer processing. The etching rates of polycrystalline silicon (poly-Si) and SiO 2 across the wafer were evaluated as a function of ECR position. Two-dimensional (radial and vertical) distributions of the ion flux in the reactor were also investigated using a movable single probe system. A ring-shaped region of highdensity plasma along the ECR plane was observed. This reveals the mechanism that the etching-rate distribution could be controlled by the ECR position. As a result, a polycrystalline silicon etching rate uniformity of 1.5% across a wafer was successfully obtained. Furthermore, the uniformity control of critical dimensions (CDs) based on wafer temperature was also investigated, and CD uniformity below 3 nm across the wafer was obtained in the optimum temperature distribution. #

A two-region model for azimuthal striations in an inductively coupled plasma

“…Inductively coupled plasmas (ICPs) are widely used in the semiconductor industry [1]. One of the most important concerns in this industry is processing uniformity, which is related to plasma uniformity across the wafer surface in both the radial and azimuthal directions [2]. For a cylindrical ICP, researchers often prioritize radial plasma uniformity [3,4], as plasma is generally assumed to be uniform in the azimuthal direction owing to the axial symmetry of the electric field.…”

(Invited) Plasma Etching Technology Challenges for Future CMOS Fabrication Based on Microwave ECR Plasma

“…During low-pressure operation (sub-Pa level), it was found that directional etching was achieved with reduced reactive ion etching (RIE) lag and critical dimension (CD) bias. Recently, good uniformity was confirmed in 450 mm wafer etching processes (5). In the 1980s and 1990s, a number of sophisticated etching functions were investigated, including gas pulsing (6), pulsed discharge (7), wafer radio-frequency (RF) pulsing (8,9), atomic layer control (10,11), and electron beam plasma (12).…”