Article: "Plasma etching of Al and Cu oxides"

The process of etching the material is an integral part of the production of semiconductor devices. There is a "dry" etching method using low-pressure ion-plasma treatment plants [1]. Due to plasma treatment, the etching of the material occurs without harmful effects on the environment compared to the liquid etching method [2].

To carry out etching to a certain thickness, it is necessary to know the etching rate, which depends on the material being processed, the gas medium, pressure, plasma power, as well as time [3].

In this article, the rate of ion-plasma etching of aluminum oxide films Al2O3 and Cu copper deposited on quartz resonators is investigated. The thickness control was carried out on the basis of the method of measuring the thickness of the film with quartz resonators [4].

The thickness change after spraying and etching processes was measured using quartz resonators. Knowing the nominal resonant frequency of quartz and the frequency change after processing, it is possible to calculate the change in specific gravity on the surface of the electrodes. If, after processing, the frequency of the quartz resonator increases, then the specific mass of the material on the surface of the electrodes decreases; if the frequency decreases, then the specific mass increases. The change in mass shows how much the thickness of the film has changed. Using the Sauerbry equation, which converts the frequency of a quartz resonator into mass, changes in the specific mass were found after applying the film and after etching [5]. Since the etching rate is defined as the thickness of the etched material per unit time, the specific gravity was converted to the thickness of the film, using the processing time and the density of the material.

Based on the experiments carried out, graphs of the dependence of the etching rate on time V(t) and the film thickness on time h(t), as well as the relative change in the frequency of quartz resonators on time δ(t) are plotted, shown in Fig. 1, 2, respectively.
chart with tatya.PNG
Graph of the dependence of the relative frequency change of quartz resonators on time

The experimental data showed that over time the etching rate of the copper film decreases, and during the repeated processing of the same quartz resonator with the same processing mode, the etching of the film does not occur. The maximum etching speed is 2.72 nm/min. Etching of the AL2O3 film occurs only at a time interval of 1-1.5 min and more than 2 min. At the interval of 1.5–2 min, the mass of the quartz resonator increases, which is associated with the oxidation process of Al.
The dependence of the relative frequency change on time δ(t) is similar to the dependence of thickness on time h(t). Minimal changes occurred for copper at 1.5 min. In the case of Al2O3, the graph δ(t) has negative values, which also indicates that the etching process does not occur at this interval.

Link to the article in the journal: https://tech-e.ru/mrs.php

Literature

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2. Pavlenko A.D., Rogozhin A. A., Vasiliev D. D. Influence of physical and geometric parameters of the plasma treatment plant on the wettability angle of the glass substrate. 11th All-Russian Conference of Young Scientists and Specialists "The Future of Russian Mechanical Engineering" Bauman Moscow State Technical University, MT-11, September 24-27
3. Wayne M. Moreau. Semiconductor lithography: Principles, methods and materials. Sri Lankan International Menlo Park, California, 1988.
4. Sauerbrei G. Verwendung von Schwingkwarzen zur Wagung danner Schichten and zur Microwagung. Institute of Physics and Technology of the University of Berlin, 1959.
5. Wang X., Li M., Long S. S. Memory from the Sauerbrey equation: The case of the microbalance of a quartz crystal with a coating in terms of ammonia. Hindawi Publishing Corporation "Mathematical Problems in Engineering", 2011.