Uniformity of Etching in Parallel Plate Plasma Reactors

Abstract

A two~dimensional transport and reaction model of a high pressure (-1 torr) high frequency (13.56 MHz) single-wafer parallel plate plasma reactor was developed. The chemical etching uniformity was studied as a function of reactor operating conditions. The ratio of the reactivity of the surrounding electrode surface as compared to that of the wafer surface, S, critically affected uniformity. A bullseye clearing pattern was predicted for S < 1, and the reverse pattern for S > 1, while etching was uniform for S = 1. In the case of S ~ 1, and for the parameter range studied, the absolute uniformity was found to improve by surrounding the wafer with a material of similar reactivity, by increasing the flow rate, or by decreasing the reactor pressure or power. However, such actions also served to decrease the etch rate. The oxygen plasma was used as a model experimental system to test the theoretical predictions. An experimental technique based on spatially resolved optical emission spectroscopy in concert with actinometry and the Abel transform was developed to obtain a three-dimensional mapping of the reactant (O atom) concentration profile in the plasma reactor. When a reactive film was covering part of the substrate electrode, a profound decrease in the reactant concentration was observed over the film. At the same time, large concentration gradients developed, especially at the boundary of the reactive film with the surrounding electrode. Good quantitative agreement was found between the model predictions and the experimental reactant concentration data for the range of pressure, power, flow rate, and reactive film radius examined.

A Mathematical Model for Etching of Silicon Using CF 4 in a Radial Flow Plasma Reactor

“…Hence the excess fluorine diffuses toward the reactive surface serving to enhance the etching rate around the outer periphery of the reactive surface. This phenomenon is entirely similar to the local loading effect observed in single-wafer etchers (18,10) and in downstream etching reactors (19).…”

“…In addition, the local loading effect at the downstream edge of the etching surface becomes increasingly important with increasing temperature. This is because of the greater disparity in reactivity between the etching surface and the surrounding electrode (18). The uniformity index as a function of temperature is shown in Fig.…”

Feedback control of plasma etching reactors for improved etching uniformity

“…;10 cm\ "1.7756;10\ kg s\ cm\ "2.171;10\ kg cm\ 1 "8.292;10\ mol A\ cm\ (for a more detailed analysis the reader may refer to Armaou & Christo"des (1999) and Economou, Park, & Williams (1989), under the assumption that the velocity in the z-direction, v X , is only a function of z:…”

Simulation-Based Optimization of a Vector Showerhead System for the Control of Flow Field Profile in a Vertical Reactor Chamber

“…Employing computational fluid dynamic (CFD) method is more and more favored by the researchers and engineers because of its efficiency and economy compared with the trial-and-error process experiment. From the view of the research achievements and experiences on the process mechanism in some typical reactors [4][5][6][7][8][9][10][11][12][13][14][15], the essential problem, which should be considered for the design of showerhead gas delivery system, is how to control the gas mass transport in the reactor, make the spatial distribution profile of reaction precursors meet a certain special requirement, and achieve the expected process uniformity in the final. From the view of chemical pathway and reaction analysis model of plasma enhanced chemical vapor deposition (PECVD) and thermal chemical vapor deposition (CVD) etcaeteras [9,13,15], we can deduce that a uniform chemical reaction on the wafer surface needs the factors of temperature distribution, reaction gas concentration distribution, resident time, and chemical 2 Advances in Mechanical Engineering reaction rate to achieve a certain coordination in the spatial domain over the wafer.…”