Properties of SiO 2 Films Fabricated by Microwave Ecr Plasma Processing with and Without Energetic Particle Bombardment
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PROPERTIES OF Si0 2 FILMS FABRICATED BY MICROWAVE ECR PLASMA PROCESSING WITH AND WITHOUT ENERGETIC PARTICLE BOMBARDMENT DURING FILM DEPOSITION PART I. FABRICATION PROCESSES AND PHYSICAL PROPERTIES T.T CHAU, S. R. MEJIA, and K. C. KAO Materials and Devices Research Laboratory, Department of Electrical and Computer Engineering, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2.
ABSTRACT
Silicon dioxide (SiO2 ) films were fabricated by microwave ECR plasma processing. Two groups of films were fabricated; group A with the substrates placed in a position directly facing the plasma so that the substrates as well as the on-growing films were subjected to bombardment of energetic particles produced in the plasma, and group B with the substrates placed in a processing chamber physically separated from the plasma chamber in order to prevent or suppress the damaging effects resulting from these energetic particle bombardment. The systems used for fabricating these two different groups of samples are described. The films were deposited at various deposition temperatures. On the basis of the deposition rate as a function of deposition temperature the film growth for group A samples is due mainly to mass-limited reaction, and that for group B samples is due to surface rate limited reaction. The stoichiometric level for group A does not change with deposition temperature though the films density increases with increasing deposition temperature. However, group B samples exhibit an off-stoichiometric property but they become highly stoichiometric as the deposition temperature is increased beyond 200 *C
TINRODUCTION
Plasma processing of materials has been extensively used in microelectronic fabrication because it involves only low temperatures (5400 'C), which reduces the thermal budget that is vital to the submicron technology. Plasma processing, either for thin film deposition or for etching, can be performed within a closed system, minimizing foreign particle contamination and preventing harmful chemical waste from leaking out to the environment. However, in plasma processing there are still some problems such as the damage of the SiO 2 film by the energetic electrons, ions, or photons produced in the plasma during deposition[ 1,2], the heterogeneous gas phase reaction to form dust particles on the substrate and the growing film surfaces resulting in the formation of weak spots inside the bulk of the deposited films, etc. Recently, microwave electron cyclotron resonance (ECR) plasma processing has been extensively studied for use in thin film deposition and etching. Under ECR conditions plasma can be formed at low pressures (- 10-4 torr) with a high degree of ionization and low energy levels of ions and electrons. However, although the average energy of electrons and ions may be small, there are energetic electrons and ions as well as photons in the plasma that may cause damage by their bombardment on the substrates or the on-growing films. The purpose of this paper is to present a method for preventing those plasma
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